Method for manufacturing prepreg

ABSTRACT

A method of manufacturing a prepreg. The method includes step (I) of dispersing a reinforcing fiber bundle to obtain a reinforcing fiber base material, step (II) of providing a binder to the reinforcing fiber base material produced in the step (I), and step (III) of hybridizing a matrix resin composed of a thermoplastic resin with the reinforcing fiber base material provided with the binder produced in the step (II), wherein the steps (I) to (II) are carried out online and the prepreg is one such that the content of the reinforcing fiber bundle relative to the whole portion of the prepreg is from 10 to 80% by mass, the content of the binder relative to the whole portion of the prepreg is from 0.1 to 10% by mass, and the content of the matrix resin relative to the whole portion of the prepreg is from 10 to 80% by mass.

This application is a division of application Ser. No. 12/737,619, filedJan. 31, 2011, which is a 371 of international applicationPCT/JP2009/063240, filed Jul. 24, 2009, which claims priority based onJapanese Patent Application Nos. 2008-197812, 2008-198456, 2008-198457and 2008-198458 filed Jul. 31, 2008, and Japanese Patent Application No.2009-085469 filed Mar. 31, 2009, and which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to prepregs in which a reinforcing fiberbase material has been impregnated with a resin, and a preform producedby laminating them. Particularly, it relates to prepregs in whichreinforcing fibers have a specific two-dimensional orientation angle andwhich have a specific thickness, and to a preform produced by laminatingthem. Moreover, the present invention relates to a method formanufacturing a prepreg.

BACKGROUND ART

Fiber reinforced plastics (FRP) are light in weight and have superiormechanical properties and therefore are used widely for electrical orelectric instrument applications, civil engineering or buildingapplications, machine or mechanical component applications, robotapplications, motorcycle or automobile applications, universal or aerialapplications, etc. As reinforcing fibers to be used for such FRP, therehave been used metal fibers, such as aluminum fibers and stainless steelfibers, organic fibers, such as aramid fibers and PBO fibers, inorganicfibers, such as silicon carbide fibers, and carbon fibers. Among these,carbon fiber is preferably used from the viewpoint of being excellent inspecific strength and specific rigidity and being capable of affordingexcellent lightness.

Here, one example of representative FRP like carbon fiber-reinforcedplastics (CFRP) is a molded product produced by subjecting a preformobtained by laminating prepregs to press molding (a molding methodcomprising defoaming and shaping performed under pressurization).Prepregs are commonly produced by a method comprising impregnating areinforcing fiber base material prepared by arraying in one direction orweaving continuous reinforcing fibers with a resin.

Superior mechanical properties can be obtained with molded productsprepared by using such prepregs. On the other hand, since reinforcingfibers are used in their original continuous form, they are unsuitablefor shaping into a complicated shape. Moreover, since the laminationangle of prepregs has a great influence on properties, it is necessaryto laminate prepregs by paying attention of the lamination angle. Inother words, since a lamination step requires time and effort and thecost increases accordingly (i.e., an economic burden caused by thelamination step will increase), usage is restricted.

Patent document 1 proposes a prepreg that is effective for shaping intoa complicated shape by cutting reinforcing fibers into a specificlength. However, since a lamination step requires time and effort likethat mentioned above, an economic burden has not been eliminated.

On the other hand, FRPs using discontinuous reinforcing fibers have alsobeen proposed. Sheet molding compounds (SMC) and glass mat basematerials (GMT) are materials suitable for press molding. However, theirusage is restricted because their mechanical properties, such asspecific strength and specific rigidity, are poor, they are difficult tobe applied to thin molded products, and isotropic mechanical propertiesare hardly obtained because resin flows very much at the time ofmolding, and their characteristics vary widely.

Patent documents 2, 3 each propose a sheet material in which moreisotropic properties can be obtained by dispersing reinforcing fibers ina bundle form. In patent document 4 is proposed a sheet material withsuperior mechanical properties caused by uniform dispersion of carbonfibers. However, since all of them cannot be processed to be thin like aprepreg and resin flows greatly at the time of shaping, an isotropicproperty may be impaired, and mechanical properties may also decline.

Moreover, in patent document 5 is proposed a molded product in whichcarbon fibers have been fixed while being randomly dispersed in the formof single yarn. Also in this method, there is a limit in processing itto be thin and therefore the degree of freedom of lamination of apreform is restricted. Furthermore, since it is impossible to produce alarge number of preforms, an economic burden has not been eliminated.

PRIOR ART DOCUMENTS Patent Documents

-   Patent document 1: JP 2007-146151 A-   Patent document 2: Japan Patent No. 2507565-   Patent document 3: Japan Patent No. 1761874-   Patent document 4: JP 6-99431 A-   Patent document 5: WO2007/097436

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In considering the background of the conventional technologies, anobject of the present invention is to provide a prepreg that can beapplied to a thin molded product for which laminated molded productshave been unsuitable and is superior in isotropic mechanical propertiesand that can afford a molded product with a complicated shape, and apreform.

Means for Solving the Problems

The prepreg of the present invention is a prepreg comprising areinforcing fiber base material impregnated with a thermoplastic resin,wherein the reinforcing fiber base material comprises from 0 to 50% bymass of reinforcing fibers each having a fiber length of more than 10mm, from 50 to 100% by mass of reinforcing fibers each having a fiberlength of from 2 to 10 mm, and from 0 to 50% by mass of reinforcingfibers each having a fiber length of less than 2 mm, and the average oftwo-dimensional orientation angles each formed by a reinforcing filament(a) contained in the prepreg and a reinforcing filament (b) intersectingthe reinforcing filament (a) is from 10 to 80°, the thickness h0 (mm) at23° C. is 0.03 to 1 mm, and the tensile strength σ is 0.01 MPa or more.

Moreover, the preform of the present invention is a preform comprisingat least, as a lamination unit, a prepreg which comprises a reinforcingfiber base material impregnated with a thermoplastic resin and in whichthe average of two-dimensional orientation angles each formed by areinforcing filament (a) and a reinforcing filament (b) intersecting thereinforcing filament (a) is from 10 to 80°, the thickness h0 (mm) at 23°C. is 0.03 to 1 mm, and the tensile strength σ is 0.01 MPa or more.

Effect of the Invention

Since reinforcing fibers have a specific fiber length and a specifictwo-dimensional orientation angle in the prepreg of the presentinvention, no great restriction due to a lamination angle is caused inlaminating prepregs and a molded product that is isotropically superiorin mechanical properties can be obtained. The prepreg of the presentinvention can be applied to thin molded products for which conventionallaminated molded products have been unsuitable by making it to have aspecific thickness and, in addition, it can reduce the proportion ofreinforcing fibers in the in-layer thickness direction, so that it canenhance an in-plane reinforcing effect. Moreover, the prepreg of thepresent invention is superior in workability at the time of laminationand is effective in application to a wide variety of uses because of itspossession of a specific tensile strength.

Moreover, since reinforcing fibers contained in prepregs have specifictwo-dimensional orientation angles and the prepregs are made to have aspecific thickness, the preform of the present invention can reduce theproportion of reinforcing fibers in the thickness direction, can reducethe interference between layers, and can increase the shapability inpress molding. Thereby, it is possible to obtain a molded product thatsatisfies moldability of a complicated shape and mechanical properties,which was unsuitable for conventional laminated molded products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating one example of the dispersionstate of reinforcing fibers in the prepreg of the present invention.

FIG. 2 is a schematic diagram illustrating one example of a burning jigfor measuring the two-dimensional orientation angle of a prepreg.

FIG. 3 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 4 is a schematic diagram illustrating one example of a box-shapedproduct that is obtainable by the use of the prepreg and the preform ofthe present invention.

FIG. 5 is a schematic diagram illustrating one example of a box-shapedproduct that is obtainable by the use of the prepreg and the preform ofthe present invention.

FIG. 6 is a schematic diagram of lamination using a prepreg of thepresent invention and GMT.

FIG. 7 is a schematic diagram of a cut-in carbon fiber prepreg.

FIG. 8 is a schematic diagram of a molded automobile bonnet.

FIG. 9 is a schematic diagram illustrating one example of the apparatusfor manufacturing a prepreg.

FIG. 10 is a schematic diagram illustrating one example of the apparatusfor manufacturing a prepreg.

FIG. 11 is a schematic diagram illustrating one example of the apparatusfor manufacturing a prepreg.

FIG. 12 is a schematic diagram illustrating one example of the apparatusfor manufacturing a prepreg.

FIG. 13 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 14 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 15 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 16 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 17 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 18 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 19 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 20 is a schematic diagram illustrating one example of thehorizontally-viewed positional relationship of a dispersion vessel, apapermaking vessel, and a transport portion.

FIG. 20 is a schematic diagram illustrating one example of the sectionalshape of a transport portion.

FIG. 22 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 23 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 24 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 25 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 26 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 27 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 28 a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 29 is a schematic diagram illustrating one example of the apparatusfor manufacturing a reinforcing fiber base material (papermaking basematerial).

FIG. 30 is a schematic diagram of a slurry containing reinforcingfibers.

MODE FOR CARRYING OUT THE INVENTION

The prepreg of the present invention is a prepreg comprising areinforcing fiber base material impregnated with a thermoplastic resin,wherein the reinforcing fiber base material comprises from 0 to 50% bymass of reinforcing fibers each having a fiber length of more than 10mm, from 50 to 100% by mass of reinforcing fibers each having a fiberlength of from 2 to 10 mm, and from 0 to 50% by mass of reinforcingfibers each having a fiber length of less than 2 mm, and the average oftwo-dimensional orientation angles each formed by a reinforcing filament(a) and a reinforcing filament (b) intersecting the reinforcing filament(a) is from 10 to 80°, the thickness h0 (mm) at 23° C. is 0.03 to 1 mm,and the tensile strength a is 0.01 MPa or more. First, theseconstituents are explained.

[Reinforcing Fiber Base Material]

The reinforcing fiber base material in the present invention means aprecursor which has been processed into the form of sheet, fabric, orweb. The reinforcing fiber base material is not particularly limitedwith respect to its form or shape if it has, between reinforcing fibers,voids into which resin penetrates. For example, it is permissible thatthe reinforcing fibers have been mixed with organic fibers, an organiccompound, or an inorganic compound, that the reinforcing fibers havebeen sealed with another component, or that the reinforcing fibers havebeen bonded to a resin component. From the standpoint of easilymanufacturing the two-dimensional orientation of reinforcing fibers inthe present invention, a base which is in a nonwoven fabric formobtainable by a dry process or a wet process and in which reinforcingfibers have been opened and the reinforcing fibers have been sealedtogether with an organic compound can be provided as an example of apreferable shape of the reinforcing fiber base material.

Moreover, it is preferable that the reinforcing fiber base material tobe used in the present invention hold voids sufficient for making aresin component, which will become a matrix, to penetrate thereinto, andfor this reason, it is preferable to make the reinforcing fiber basematerial to secure gas permeability. The gas permeability can bemeasured, for example, by the Gurley type tester method based on JISP8117 or the Frazier type method based on ASTM D737. Of these, it ispreferred to use the amount of air (cm³/cm²·s) determined by the Fraziertype method based on ASTM D737 as a measure for the purpose ofevaluating a material that is better in gas permeability. A preferableamount of air to be determined by the Frazier type method based on ASTMD737 is 50 or more, more preferably 70 or more, and particularlypreferably 100 or more. Although the upper limit of the amount of air isnot particularly restricted, an amount of 1000 or less can generally beprovided as an example.

[Reinforcing Fiber]

The reinforcing fibers to be used for the prepreg of the presentinvention are not particularly restricted and, for example, carbonfibers, glass fibers, aramid fibers, alumina fibers, silicon carbidefibers, boron fibers, metal fibers, natural fibers, and mineral fiberscan be used. These kinds of fiber may be used singly or two or morekinds of fibers may be used in combination. In particular, from theviewpoint of weight reduction, carbon fibers of PAN type, pitch type,rayon type, or the like are preferably used because they are high instrength and specific rigidity. From the viewpoint of increasing theeconomical efficiency of a molded product to be obtained, glass fibersare preferably used, and it is preferable to use carbon fibers and glassfibers together in combination from the viewpoint of the balance betweenmechanical properties and economical efficiency. From the viewpoint ofincreasing the impact absorbability or the shapability of a moldedproduct to be obtained, aramid fibers are preferably used, and it ispreferable to use carbon fibers and aramid fibers together incombination from the viewpoint of the balance between mechanicalproperties and impact absorbability. Moreover, from the viewpoint ofincreasing the electroconductivity of a molded product to be obtained,it is also permissible to use reinforcing fibers coated with metal, suchas nickel, copper, and ytterbium.

[Carbon Fiber]

Carbon fibers are preferably those with a surface oxygen concentrationratio O/C measured by the X-ray photoelectron spectroscopy of from 0.05to 0.5, more preferably from 0.06 to 0.3, and even more preferably from0.07 to 0.2. When the surface oxygen concentration ratio is 0.05 ormore, the amount of polar functional groups of the surface of carbonfibers is secured and the affinity with a thermoplastic resincomposition becomes high and, therefore, stronger adhesion can beachieved. When the surface oxygen concentration ratio is 0.5 or less, itis possible to reduce the fall of the strength of carbon fibers causedby surface oxidation.

The surface oxygen concentration ratio means the atomic number ratio ofoxygen (O) to carbon (C) of the fiber surface. The procedure in whichthe surface oxygen concentration ratio is determined by X-rayphotoelectron spectroscopy is explained below with reference to oneexample. First, a seizing agent or the like sticking on the carbon fibersurface is removed. Subsequently, the carbon fibers are cut into 20 mmand are spread and arranged on a copper sample support. Then, the insideof a sample chamber is held at 1×10⁸ Torr by the use of A1Kα1, 2 as anX-ray source. The kinetic energy value (K.E.) of the primary peak ofC_(1s) is adjusted to 1202 eV as a correction value of a peakaccompanying the electrification at the time of measurement. The area ofthe C_(1s) peak is determined by drawing a straight baseline within arange of from 1191 to 1205 eV in K.E. The area of the O_(1s) peak isdetermined by drawing a straight baseline within a range of from 947 to959 eV in K.E.

The surface oxygen concentration ratio is a value calculated as anatomic number ratio from the ratio of the O_(1s) peak area and theC_(1s) peak area using a sensitivity correction value that is inherentto an instrument. It can be calculated by using Model ES-200manufactured by International Electric Co., Ltd., as an X-rayphotoelectron spectrometer and using 1.74 as a sensitivity correctionvalue.

The means for controlling the surface oxygen concentration O/C of carbonfibers to be from 0.05 to 0.5 is not particularly restricted andexamples thereof include such techniques as electric field oxidationtreatment, chemical solution oxidation treatment, and vapor phaseoxidation treatment. Among these, the electric field oxidation treatmentis preferred because it is easy to handle.

As an electrolytic solution to be used for electric field oxidationtreatment, aqueous solutions of compounds listed below are suitablyused. The compounds include inorganic acids, such as sulfuric acid,nitric acid, and hydrochloric acid, inorganic hydroxides, such as sodiumhydroxide, potassium hydroxide, and barium hydroxide, ammonia, inorganicmetal salts, such as sodium carbonate and sodium hydrogen carbonate,organic salts, such as sodium acetate and sodium benzoate, potassiumsalt, barium salts, other metal salts, and ammonium salts instead ofthese sodium salts, and organic compounds such as hydrazine. Amongthese, inorganic acids are preferred as an electrolytic solution, andsulfuric acid and nitric acid are used particularly preferably.Regarding the degree of electric field treatment, the O/C of the carbonfiber surface can be controlled by determining the amount of electricitywhich flows during the electric field treatment.

[Prepreg]

The prepreg of the present invention can hold its shape as a prepreg bythe penetration of a resin into the voids of the aforementionedreinforcing fiber base material. In addition, a preform can be producedby laminating the prepregs with stability while the reinforcing fibersare fixed. That is, the time and effort in a lamination process can bereduced and thereby an economic burden can be reduced. Particularly fromthe viewpoint of improving the handling performance of prepregs in thelamination of the prepregs and further reducing the time and effort forwork, it is important to adjust the orientation of the reinforcingfibers to within a specific range. This can prevent interference in thethickness direction and therefore can secure the isotropy of a moldedproduct even if prepregs are laminated simply. Moreover, the adjustmentof the length of reinforcing fibers to within a specific range not onlyresults in that a molded product to be obtained is superior inmechanical properties, but it also makes it possible to inhibit thethickness expansion of prepregs or a preform obtained by laminating theprepregs and allow them to be transferred without any size or shapelimitations and be subjected to a molding process.

The “isotropy” as referred to herein means that when a prepreg or apreform produced by laminating prepregs is processed into a moldedproduct, the molded product exhibits uniform characteristics, such asspecific strength, specific rigidity, and coefficient of linearexpansion, regardless of the direction in the plane of the moldedproduct.

Here, it is important that the reinforcing fiber base material in thepresent invention is composed of from 0 to 50% by mass of reinforcingfibers having a fiber length exceeding 10 mm, from 50 to 100% by mass ofreinforcing fibers having a fiber length of from 2 to 10 mm, and from 0to 50% by mass of reinforcing fibers having a fiber length of less than2 mm. If the amount of the reinforcing fibers having a fiber lengthexceeding 10 mm exceeds 50% by mass, the thickness expansion in alamination process or a molding process may become large and thehandling performance may be impaired. If the amount of reinforcingfibers having a fiber length of less than 2 mm exceeds 50% by mass, notonly the mechanical properties of a molded product to be obtained maydeteriorate, but also a prepreg or a preform to be obtained bylaminating prepregs cannot secure sufficient strength and, as a result,the moldability may be impaired. From these viewpoints, it is preferablethat the reinforcing fiber base material comprise from 80 to 100% bymass of reinforcing fibers having a fiber length of from 3 to 8 mm.Moreover, it is more preferable that the distribution of the fiberlength of the reinforcing fiber base material have at least two peaksand at least one peak be within a fiber length range of from 5 to 10 mmand at least one peak be within a fiber length range of from 2 to 5 mm.By bringing the distribution of the fiber length into such a morepreferable range, it is possible to use reinforcing fibers for securingmechanical properties and reinforcing fibers for securing handlingperformance of a preform in a lamination process or a molding processtogether and to easily reconcile the characteristics of both types ofreinforcing fibers. The mass percentage of reinforcing fiber referred toherein indicates the percentage of the fiber length in number averagewhen the amount of all the reinforcing fibers forming the reinforcingfiber base material is 100% by mass.

Examples of the method for measuring the fiber length of reinforcingfibers include a method in which reinforcing fibers are removed directlyfrom a reinforcing fiber base material, and a method in which the resinof a prepreg is dissolved by using a solvent which can dissolve only theresin and the remaining reinforcing fibers are collected by filtrationand measured by microscopic observation (a dissolution method). In acase where no solvent can dissolve the resin, a method is availablewhich comprises burning off only the resin within a temperature rangewhere reinforcing fibers do not lose their weight due to oxidation toisolate the reinforcing fibers and measuring them by microscopicobservations (a burning off method). The measurement can be done byselecting 400 reinforcing fibers at random, measuring the length thereofdown to 1 μm by using an optical microscope, and then measuring thefiber lengths and the proportions thereof. When comparing a method ofextracting reinforcing fibers directly from a reinforcing fiber basematerial to a method of extracting reinforcing fibers from a prepreg bya burning off method or a dissolving method, no particular differencewill occur between the results to be obtained if conditions are selectedappropriately.

Moreover, the orientation of the reinforcing fibers in the presentinvention can be defined by a two-dimensional orientation angle.Generally, a reinforcing fiber base material is often composed ofreinforcing fibers in the form of a bundle, and therefore it isdifficult to secure isotropy as a prepreg, and the penetration of resininto a bundle is insufficient and this may cause decrease in strength ofa molded product. Even if a reinforcing fibers bundle is disperses intosingle yarns, a similar result will be produced if the single yarns ofreinforcing fibers come into contact with each other in parallel.Moreover, the fiber orientation in the thickness direction may cause theexpansion of the thickness of a prepreg or a preform to be obtained bylaminating prepregs and it may remarkably impair handling performanceand moldability.

Here, the two-dimensional orientation angle formed by a reinforcingfilament (a) and a reinforcing filament (b) that intersects thereinforcing filament (a) in the present invention is explained withreference to a drawing. FIG. 1 is a schematic diagram illustrating adispersion state of reinforcing fibers observed when only reinforcingfibers of one example of the prepreg of the present invention areobserved from the plane direction. When reinforcing filament 1 isselected, reinforcing filament 1 intersects reinforcing filaments 2 to7. The intersection as referred to herein means a state where aparticular reinforcing filament (a) is observed to intersect anotherreinforcing filament (b) in a two-dimensional plane observed. In anactual prepreg, reinforcing fiber 1 is not necessarily required to be incontact with reinforcing fibers 2 to 7. The two-dimensional orientationangle is defined as an angle 8 measuring from 0 to 90° of the two anglesformed by two crossed reinforcing filaments.

Although there is no restriction with the method for concretelymeasuring the average value of two-dimensional orientation angles from aprepreg, a method that comprises observing the orientation ofreinforcing fibers from the surface of a prepreg can be provided as anexample. In this case, it is preferable to grind the surface of theprepreg to expose fibers because it becomes easier to observe thereinforcing fibers. Another example is a method that comprises observingthe orientation of reinforcing fibers by applying transmitted light to aprepreg. In this case, it is preferable to slice the prepreg because itbecomes easier to observe the reinforcing fibers. Still another exampleis a method that comprises observing a prepreg by X-ray CT transmissionto photographing an image of the orientation of reinforcing fibers. Inthe case of reinforcing fibers with high transparency to X-ray, it ispreferable to mix fibers for a tracer with the reinforcing fibers or toapply a chemical agent to the reinforcing fibers because it becomeseasier to observe the reinforcing fibers.

When it is difficult to perform measurement by the aforementionedmethods, a method that comprises removing a resin while not destroyingthe structure of reinforcing fibers and then observing the orientationof the reinforcing fibers can be provided as an example. For example, asillustrated in FIG. 2( a), measurement can be performed by sandwiching aprepreg between two sheets of stainless steel mesh, fixing them withscrews or the like so that the prepreg might be prevented from moving,then burning resin components off, and observing the resultingreinforcing fiber base material (FIG. 2( b)) with an optical microscopeor an electron microscope.

The average of two-dimensional orientation angles in the presentinvention is measured in the following procedures I and II.

I. Two-dimensional orientation angles formed by a reinforcing filament(a) selected at random (reinforcing filament 1 in FIG. 1) and each ofall reinforcing filaments (b) intersecting the reinforcing filament (a),all the reinforcing filaments (b) that intersect this reinforcingfilament (a) (reinforcing filaments 2 to 7 in FIG. 1) are measured, andtheir average value is calculated. When there are a large number ofreinforcing filaments (b) intersecting the reinforcing filament (a), anaverage value measured by selecting 20 intersecting reinforcingfilaments (b) at random may be as a substitution.

II. The measurement of I., is repeated for other reinforcing filaments(a) five times in total and the average of the measurements iscalculated as the average of two-dimensional orientation angle.

The average of the two-dimensional orientation angles of the reinforcingfibers in the present invention is from 10 to 80°, preferably from 20 to70°, and more preferably from 30 to 60°, and it is better that theaverage is closer to 45°, which is the ideal angle. That the average oftwo-dimensional orientation angles is smaller than 10° or larger than80° means that many reinforcing fibers remain in the form of a bundle,and it results in deterioration of mechanical properties. Moreover, whentwo-dimensional isotropy is impaired, it is necessary to laminate manyprepregs so that the orientation of reinforcing fibers are arranged inrespective directions in order to secure the isotropy of the propertiesof a molded product. When reinforcing fibers of the thickness directioncannot be ignored, it becomes difficult to handle, for example, arrangeor transfer, prepregs in laminating them, so that the economic burden ina lamination process may increase.

The two-dimensional orientation angle can be made closer to an idealangle by dispersing reinforcing fibers and arranging them planarly whenmanufacturing a reinforcing fiber base material. In order to increasethe degree of the dispersion of the reinforcing fibers, a dry process ora wet process can be used. The dry process is a method in the dispersionof a reinforcing fiber bundle is performed in the air. The wet processis a method in the dispersion of a reinforcing fiber bundle is performedin water. As to the dry process, a method of providing a filamentationbar, a method of vibrating a filamentation bar, a method of makingopenings of a card smaller, and a method of adjusting the rate ofrotation of a card can be provided as examples. As to the wet process, amethod of adjusting stirring conditions in dispersing reinforcingfibers, a method of reducing the concentration, a method of adjustingthe viscosity of a solution, and a method of inhibiting a whirlpool intransferring a dispersion liquid can be provided as examples.

In order to arrange reinforcing fibers planarly, a method of usingstatic electricity in when accumulating reinforcing fibers, a method ofusing a regulated air flow, and a method of adjusting the hauling rateof a conveyor can be provided as examples of the dry process. As to thewet process as well, a method of preventing reflocculation ofreinforcing fibers dispersed using an ultrasonic wave or the like, amethod of adjusting the filtration rate, a method of adjusting the meshdiameter of a conveyor, a method of adjusting the hauling rate of aconveyor can be provided as examples. These methods are not particularlylimited and can be achieved also by controlling other manufactureconditions while checking the state of a reinforcing fiber basematerial.

Particularly when the manufacture is performed by the wet process, amethod of using an apparatus for manufacturing a papermaking basematerial as illustrated in FIG. 3 can be provided as an example. Thebasis weight of the reinforcing fiber base material to be obtained canbe increased by increasing the concentration of fibers to be charged.Moreover, the basis weight can be adjusted also by adjusting the rate offlow (flow rate) of a dispersion liquid and the speed of a meshconveyor. For example, the basis weight of a reinforcing fiber basematerial to be obtained can be increased by increasing the rate of flowof the dispersion liquid while fixing the speed of the mesh conveyor.The basis weight of the reinforcing fiber base material to be obtainedcan be obtains conversely by reducing the rate of flow of the dispersionliquid while fixing the speed of the mesh conveyor. Furthermore, it isalso possible to control the orientation of fibers by adjusting thespeed of the mesh conveyor relative to the rate of flow of thedispersion liquid. For example, if the speed of a mesh conveyor isincreased relative to the rate of flow of a dispersion liquid, theorientation of the fibers in a reinforcing fiber base material to beobtained becomes prone to match the hauling direction of the meshconveyor. As mentioned above, the manufacture of a reinforcing fiberbase material can be performed by adjusting various parameters.

From the viewpoint of reconciling the physical characteristics andmoldability, the mass percentage of the reinforcing fiber base materialsin the prepreg of the present invention is preferably from 5 to 60% bymass relative to 100% by mass of the prepreg, more preferably from 10 to60% by mass, even more preferably from 10 to 50% by mass, andparticularly preferably from 15 to 40% by mass. In the prepreg of thepresent invention, although the resin is required to be penetrated intovoids of the reinforcing fiber substrate, the impregnation ratio ispreferably from 30 to 100%, more preferably from 40 to 100%, and evenmore preferably from 50 to 100%. If the impregnation ratio is within thepreferable range, it can be used without impairing the handleability andthe moldability of the prepreg, which are the effects of the presentinvention. From the viewpoint of improving the weight reduction of themolded product to be obtained by using the prepreg of the presentinvention, the volume ratio of the reinforcing fibers determined whenthe impregnation ratio of the resin is converted to 100% is preferablyup to 50%, more preferably up to 40%, and even more preferably from 10to 30%.

The impregnation ratio is not particularly restricted with respect toits measuring method and can be measured by, for example, simple methodsthat are provided below. Examples include a method that comprisesobserving a section of a prepreg first, calculating the total area ofvoids on the basis of a microscopic photograph, and dividing it by thearea of the reinforcing fiber base material, a method that comprisesdetermining it from the ratio (hc0/h0) of the thickness h0 of a prepregat 23° C. to the thickness hc0 at 23° C. after press molding it, and amethod that comprises determining it from the ratio of the theoreticaldensity calculated from the used ratios of respective materials to thebulk density of the prepreg. Here, the method of calculating byobserving a section of a prepreg in the thickness direction andmeasuring the area of void portions in the section and the area of theentire section is explained concretely. Namely, it is a method thatcomprises wrapping a prepreg with a thermosetting resin such as epoxy,polishing a surface that is a sectional end of the prepreg, observing arange of from about 500 to about 1000 μm in width with an opticalmicroscope or an electron microscope, measuring, in contrast ratio, thearea of the sites where the resin has penetrated and the area of thesites where no resin has penetrated, and calculating the resinimpregnation ratio by the following formula.

Resin impregnation ratio (%)=100×(the total area of sites where theresin has penetrated)/(the total cross sectional area of the observedsite of the prepreg exclusive of reinforcing fiber portions)

The bulk density of a prepreg can be calculated from the volume at 23°C. and the mass of the prepreg. The bulk density of the prepreg of thepresent invention is preferably from 0.8 to 1.5, more preferably from0.9 to 1.4, and even more preferably from 1.0 to 1.3. If the bulkdensity is a preferable range, a molded product using the prepreg of thepresent invention can secure sufficient lightness. For the same reason,the basis weight of the prepreg is preferably from 10 to 500 g/m², morepreferably from 30 to 400 g/m², and even more preferably from 100 to 300g/m².

As to the thickness of the prepreg of the present invention, from theviewpoint of the handleability in a step of laminating to produce apreform, the thickness h0 at 23° C. is from 0.03 to 1 mm, preferablyfrom 0.05 to 0.8 mm, and more preferably from 0.1 to 0.6 mm. If h0 isless than 0.03 mm, the prepreg may rupture, whereas if it exceeds 1 mm,the shapability may be impaired.

The prepreg of the present invention is desirable because it can betransferred to a mold with stability by inhibiting the thicknessexpansion in molding when having been processed into a preform. In astep of laminating prepregs and a step of molding a preform, it isnecessary to perform preheating from the viewpoint of controlshapability or adhesiveness. Therefore, it is preferable that thethickness hn (mm) of the prepreg at (n×100)° C. be h0≦hn≦h0×(2n+1) (n isat least one natural number selected from among 1, 2, 3, and 4), morepreferably h0≦hn≦h0×2n, and particularly preferably h0≦hn≦h0×(2n−1). Thethickness of the prepreg at (n×100)° C. can be measured by using anexisting measuring means, such as a caliper, a laser displacement meterand measurement of the thickness by photographing, after leaving at restthe prepreg for 10 minutes in an atmosphere of a temperature at whichthe measurement is to be conducted.

Here, it is meant that the larger the n is, the higher the ambienttemperature is, and the prepreg has a tendency that its thicknessexpansion increases as the ambient temperature becomes higher. This isinterference of reinforcing fibers in the thickness direction inaddition to simple volume expansion, and since this phenomenon becomesmore noticeable as the viscosity of the resin is lowered, it is higherin ambient temperature dependency. Moreover, thickness expansion causedby the decomposition or foaming of the resin to be used is alsomentioned. Therefore, as to the n, a suitable number can be chosendepending on the materials to be used.

n=1 (ambient temperature: 100° C.) is a drying temperature and a generaltemperature to be used at the time of a lamination step. From theviewpoint of reduction in load of the lamination step, it is preferablethat the thickness at this temperature be up to three times h0 becauseif so, it is possible to stably adjust the thickness of the preform tobe small. Moreover, n=2 (ambient temperature: 200° C.) is a curingtemperature of common thermosetting resins and a processing temperatureof low-melting thermoplastic resins. From the viewpoint of securinghandleability in transfer to a mold or stable shapability in a moldingstep, it is preferable that the thickness at that temperature be up tofive times h0. Moreover, n=3 (ambient temperature: 300° C.) correspondsto the upper limit of a processing temperature of common general-purposeengineering plastics. From the viewpoint that less resin decompositionoccurs and a prepreg or a preform can be handled safely and stably, itis preferable that the thickness at that temperature is up to seventimes h0. Finally, n=4 (ambient temperature: 400° C.) is a processingtemperature of common super engineering plastics, where otherthermoplastic resins and thermosetting resins are promoted to decomposeand the thickness expansion of a reinforcing fiber base material becomesclose to a maximum point. Therefore, from the viewpoint of reducing thearranged proportion of reinforcing fibers in the thickness direction andstable handleability of a prepreg, it is preferable that the thicknessat that temperature be up to nine times h0.

As the method of reducing the arranged proportion of reinforcing fibersin the thickness direction, the reduction can be achieved by dispersingthe reinforcing fibers and arranging them planarly as described abovewhen manufacturing a reinforcing fiber base material. In order toarrange reinforcing fibers planarly, a method of using staticelectricity when accumulating reinforcing fibers, a method of using aregulated air flow, and a method of adjusting the hauling rate of aconveyor can be provided as examples of the dry process. As to the wetprocess as well, a method of preventing reflocculation of reinforcingfibers dispersed using an ultrasonic wave or the like, a method ofadjusting the filtration rate, a method of adjusting the mesh diameterof a conveyor, a method of adjusting the hauling rate of a conveyor canbe provided as examples. A method of continuously hauling a reinforcingfiber base material while sucking it with a conveyor with maintenance ofa particularly favorable dispersion state is preferable as a method forreducing the arranged proportion of reinforcing fibers in the thicknessdirection because it is possible to produce a reinforcing fiber basematerial by forcibly pushing down the reinforcing fibers on the conveyerin synchronization with the flow of the conveyor to a direction parallelto the conveyor plane.

When the temperature of the atmosphere where measurement is to be doneis very high and it is difficult to measure directly, the measurementmay be conducted after doing treatment so as to keep a state that thethickness is stable and adjusting the temperature to a temperature atwhich the measurement can be done. For example, if the prepreg is onemade of a thermoplastic resin, the resin flows under an atmosphere of ahigh temperature that is equal to or higher than the melting point orthe softening point, but by cooling to room temperature, measurement canbe done in a state where the resin of the prepreg has been solidifiedand the thickness has been fixed.

As to the sites for measuring the thickness, two points X and Y in aprepreg are determined so the straight distance XY might be the longestin the plane of the prepreg.

Next, the straight line XY is divided into ten or more equal parts andthe respective dividing points except both ends X, Y are determined tobe points for measuring the thickness. The average of the thicknesses atthe respective measuring points is defined as the thickness of theprepreg.

[Resin]

The resin to be used for a prepreg is not particularly restricted if itis a resin that has an ability of penetrating into a reinforcing fiberbase material and can achieve a tensile strength sufficient for securinghandleability in a lamination step, and thermoplastic resins and uncuredthermosetting resins described below can be used. Among these, athermoplastic resin is used for the prepreg of the present invention.

As to the tensile strength σ for securing handleability in a laminationstep, the higher the value is, the more suitably it can be subjected toa lamination step and a molding step of high speed and high economicalefficiency. The tensile strength σ of a prepreg is required to be atleast 0.01 MPa. If it is less than 0.01 MPa, problems, such as ruptureof a prepreg, may occur during operations of lamination or molding. Asan index of the isotropy of a prepreg, the tensile strength σ, in therelationship between the maximum tensile strength σMax and the minimumtensile strength σMin in the measuring direction, is preferablyσMax≦σMin×2, more preferably σMax≦σMin×1.8, and even more preferablyσMax≦σMin×1.5. It is preferable that the isotropy of σ be as high aspossible because the higher the isotropy of σ is, the more the economicburden in the lamination step can be reduced.

The tensile strength of a prepreg is determined by cutting specimens outfrom the prepreg, and measuring the tensile characteristic thereof inaccordance with the ISO 527-3 method (1995). Specimens were measured forfour directions, i.e., 0°, which is an arbitrary direction, +45°, −45°,and 90° directions. The number of measurements for each direction isdetermined to be n=5 or more, and the average value of all themeasurements is defined as a tensile strength. Among the tensilestrengths of the respective measuring directions, the maximum value isexpressed by σMax and the minimum value is expressed by σMin.

The thermoplastic resin to be used for the prepreg of the presentinvention may be a thermoplastic resin selected from, for example,crystalline resins including “polyesters, such as polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), polytrimethyleneterephthalate (PTT), polyethylene naphthalate (PEN) and liquid crystalpolyester, polyolefins, such as polyethylene (PE), polypropylene (PP)and polybutylene, polyoxymethylene (POM), polyamide (PA), polyarylenesulfides, such as polyphenylene sulfide (PPS), polyketone (PK),polyetherketone (PEK), polyetheretherketone (PEEK),polyetherketoneketone (PEKK), polyether nitrile (PEN), fluororesin, suchas polytetrafluoroethylene, and liquid crystal polymers (LCP),”non-crystalline resins including “styrene-based resins, polycarbonate(PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC),polyphenylene ether (PPE), polyimide (PI), polyamideimide (PAI),polyetherimide (PEI), polysulfone (PSU), polyether sulfone, andpolyarylate (PAR),” phenol-based resins, phenoxy resins, polystyreneresins, polyolefin resins, polyurethane resins, polyester resins,polyamide resins, polybutadiene resins, polyisoprene resins,fluororesins, and thermoplastic elastomers, such as acrylonitrile-basedthermoplastic elastomers, and their copolymers or modified products. Inparticular, polyolefin are preferable from the viewpoint of thelightness of a molded product to be obtained, polyamide is preferredfrom the viewpoint of strength, a non-crystalline resin, such aspolycarbonate and styrene-based resins, is preferred from the viewpointof surface appearance, polyarylene sulfide is preferred from theviewpoint of heat resistant, polyetheretherketone is preferred from theviewpoint of continuous use temperature, and fluororesins are preferablyused from the viewpoint of chemical resistance.

The use of a thermoplastic resin for the prepreg of the presentinvention is advantageous with respect to the economical efficiency in alamination step and a molding step because it will result in a hightensile strength σ. In this case, σ is preferably 1 MPa or more, morepreferably 10 MPa or more, and even more preferably 50 MPa or more.There is no particular limitations with respect to the upper limit of σ,but a general example thereof is 1000 MPa or less.

Examples of the thermosetting resin to be used for the prepreg of thepresent invention include unsaturated polyester, vinyl ester, epoxy,phenol (resol type), urea-melamine, polyimide, copolymers thereof,modified products thereof, and resins resulting from blending of two ormore of them. Particularly, epoxy resins are preferably used from theviewpoint of the mechanical properties of a molded product to beobtained. Since a prepreg is cured during a molding step, the glasstransition temperature of the thermosetting resin to be used ispreferably up to 80° C., more preferably up to 70° C., and even morepreferably up to 60° C.

If a thermosetting resin is used for a prepreg, it will become moredifficult to secure a tensile strength σ. In this case, σ is preferably0.05 MPa or more, more preferably 0.1 MPa or more, and even morepreferably 1 MPa or more. There are no particular limitations withrespect to the upper limit of σ, but a general example thereof is 10 MPaor less. The means for securing a tensile strength σ is not particularlyrestricted, and it can be achieved, for example, by a method in which ahigh viscosity type thermosetting resin is used, a method in which ahighly adhesive type thermosetting resin is used, or a method in which afiber reinforced base is sealed in advance with an organic compound orthe like.

As a resin component to be used for the present invention, a blendprepared by mixing a thermosetting resin to the aforementionedthermoplastic resin matrix. Furthermore, to the resin component mayfurther be added, according to the application, a filler, aconductivity-imparting agent, a flame retardant, a flame retardant aid,a pigment, a dye, a lubricant, a release agent, a compatibilizer, adispersing agent, a nucleating agent, a plasticizer, a heat stabilizer,an antioxidant, a coloring inhibitor, a UV absorber, a flowabilitymodifier, a foaming agent, an antibacterial agent, a damping agent, adeodorizer, a sliding property modifier, an antistatic agent, and thelike. Particularly, when the application is an electrical or electricinstrument, a car, an airplane, or the like, flame retardancy may berequired, and a phosphorus-based flame retardant, a nitrogen-based flameretardant, and an inorganic flame retardants are preferably added. Thus,when a component other than a thermoplastic resin is contained in theresin component, the content of the thermoplastic resin in the resincomponent is adjusted to be 60% by mass or more in order that the effectderived from the use of the thermoplastic resin may not be impaired.

From the viewpoint of economical efficiency, the prepreg of the presentinvention is long, and the length thereof in the longitudinal directionis preferably 500 mm or more, more preferably 800 mm or more, and evenmore preferably 1000 mm or more. There are no particular limitationswith respect to the length in the longitudinal direction, but a generalexample thereof is 4000 m or less.

[Method for Manufacturing of a Prepreg]

Various investigations have been done about the method for manufacturinga prepreg in which reinforcing fibers have been dispersed uniformly likethe prepreg of the present invention.

For example, WO 2007/97436, previously cited, discloses that when carbonfibers which are in the form of filaments, have a mass-average fiberlength of from 0.5 to 10 mm, and have a orientation parameter of from−0.25 to 0.25 are used as reinforcing fibers of a fiber-reinforcedthermoplastic resin molded product, a molded product that is superior inmechanical properties and has isotropic mechanical properties can beobtained. This fiber-reinforced thermoplastic resin molded product isproduced via (1) a step of heating and melting a thermoplastic resincontained in a molding composition, (2) a step of disposing the moldingcomposition in a mold, (3) a step of pressurizing the moldingcomposition with the mold, (4) a step of solidifying the moldingcomposition within the mold, and (5) a step of opening the mold andremoving a fiber-reinforced thermoplastic resin molded product from themold.

JP 9-94826A discloses that in manufacturing a fiber-reinforced resinsheet, it is possible to randomize fibers in a web and obtain a randomlyoriented fiber-reinforced resin sheet that is light in weight, hasisotropically high mechanical strength in respective directions, anddemonstrates superior moldability of a thin, large molded product bycontrolling the direction of the flow of a dispersion liquid containingdiscontinuous reinforcing fibers and a thermoplastic resin in processingthe dispersion liquid by papermaking.

Moreover, JP 2004-217879 A discloses, as a method for manufacturing astampable sheet, a manufacture method in which (1) reinforcing fibersand a thermoplastic resin are processed by papermaking into a sheet formby a wet dispersion process, and then they are dried to produce a webhaving a matrix structure in which the reinforcing fibers arranged in anapproximately planar direction of the sheet have been bound with thethermoplastic resin, (2) the resulting web is needled to orient some ofthe reinforcing fibers in the matrix, forming a needled mat, and (3) oneside of the needled mat is heated and pressurized at a temperature thatis equal to or higher than the melting point of the thermoplastic resinin the matrix.

In all of the methods for the manufacture of a prepreg of these patentdocuments, reinforcing fibers are processed by papermaking together witha resin, and washing of an apparatus and increasing the number ofapparatuses are needed in order to increase the number of the kind ofresin. Moreover, it is necessary to control the orientation of carbonfibers and therefore it is necessary to set up detailed conditions forevery step. Therefore, manufacture takes time and labor and there is aproblem in application to efficient manufacture of a prepreg.

Moreover, in the methods for manufacturing a prepreg disclosed in JP9-94826 A and JP 2004-217879 A, it is necessary to mix reinforcingfibers with a thermoplastic resin and it is also necessary to conductpapermaking while changing resins in order to produce molding bases ofchanged thermoplastic resins, so that much time and labor, includingwashing of a stirring vessel or a papermaking vessel or buildingmanufacture lines, will be required and therefore there are problemswith the application of these methods to efficient manufacture.

Then, it is preferable in the present invention to produce a prepreg bythe following method. That is, the method is a method for manufacturinga prepreg, the method comprising step (I) of dispersing a reinforcingfiber bundle to obtain a reinforcing fiber base material, step (II) ofproviding a binder to the reinforcing fiber base material to be producedin the step (I), and step (III) of hybridizing a matrix resin composedof a thermoplastic resin with the reinforcing fiber base materialprovided with the binder to be produced in the step (II), wherein thesteps (I) to (II) are carried out online and the prepreg is one suchthat the content of the reinforcing fiber bundle relative to the wholeportion of the prepreg is from 10 to 80% by mass, the content relativeto the whole portion of the prepreg of the binder is from 0.1 to 10% bymass, and the content relative to the whole portion of the prepreg ofthe matrix resin is from 10 to 80% by mass. According to the method ofthe present invention for manufacturing of a prepreg, it is possible toobtain in a short time a prepreg that is superior in the dispersionstate of reinforcing fibers and will demonstrate superior mechanicalproperties when being processed into a molded product.

In step (I), a reinforcing fiber bundle is dispersed to obtain areinforcing fiber base material.

The reinforcing fiber bundle means a fiber bundle that is composed ofreinforcing fibers. Although the reinforcing fiber bundle may be eitherone composed of continuous reinforcing fibers or one composed ofdiscontinuous reinforcing fibers, a discontinuous reinforcing fiberbundle is preferred for achieving a better dispersion state, and achopped fiber produced by cutting a continuous reinforcing fiber bundleare more preferable.

The reinforcing fiber bundle is preferably a fiber bundle composed ofcarbon fibers (i.e., carbon fiber bundle) and more preferably a choppedcarbon fiber.

Although there is no particular limitations with respect to the numberof filaments constituting the reinforcing fiber bundle, it is preferably24,000 or more and it is more preferably 48,000 or more, from theviewpoint of manufacture efficiency. Although there is no particularlimitations with respect to the upper limit of the number of filaments,about 300,000 filaments are much enough for keeping manufactureefficiency, dispersibility, and handling performance satisfactory inconsideration of the balance between the dispersibility and the handlingperformance.

The length of the reinforcing fiber bundle that is a raw material of areinforcing fiber base material is preferably from 1 to 50 mm, and morepreferably from 3 to 30 mm. If the length of the reinforcing fiberbundle is less than 1 mm, it may become difficult to efficientlydemonstrate the reinforcing effect caused by the reinforcing fibers. Ifthe length of the reinforcing fiber bundle exceeds 50 mm, it may becomedifficult to keep dispersion satisfactory. The length of a reinforcingfiber bundle means the length of the filaments constituting thereinforcing fiber bundle, and it can be measured by measuring the lengthof the reinforcing fiber bundle with a caliper or by taking filamentsout from the reinforcing fiber bundle and observing them with amicroscope. Moreover, in order to measure a reinforcing fiber length ina reinforcing fiber base material, it can be measured by separatingcarbon fibers from a prepreg in the following procedure. A part of theprepreg is cut out and an attached thermoplastic resin is dissolvedcompletely by using a solvent that can dissolve the thermoplastic resin.Then, carbon fibers are separated from the thermoplastic resin by knownoperations, such as filtration. Alternatively, a part of a prepreg iscut out and then heated at a temperature of 500° C. for two hours toburn off the thermoplastic resin, thereby separating carbon fibers fromthe thermoplastic resin. Four hundred carbon fibers separated areselected at random, the length thereof is measured down to 10 μm with anoptical microscope or a scanning electron microscope, and then theaverage of the measurements is defined as a fiber length.

In the step (I), either a wet process or a dry process may be used inobtaining a reinforcing fiber base material by dispersing a reinforcingfiber bundle.

When conducting the step (I) by a wet process, a reinforcing fiber basematerial can be obtained by conducting the dispersion of the reinforcingfiber bundle in water and the resulting slurry is processed bypapermaking.

As the water (dispersing water) in which the reinforcing fiber bundle isto be dispersed, waters such as normal tap water, distilled water andpurified water, can be used. If necessary, a surfactant may be mixedwith water. Although the surfactant is classified into a cationic type,an anionic type, a nonionic type, and an amphoteric type, a nonionicsurfactant is used preferably among them, and particularlypolyoxyethylene lauryl ether is used more preferably. The concentrationof the surfactant to be used when the surfactant is mixed with water isusually from 0.0001 to 0.1% by mass, and preferably from 0.0005 to 0.05%by mass.

The amount of the reinforcing fiber bundle to be added to water(dispersion liquid), which is expressed in the amount per liter of water(dispersion liquid), can be adjusted to within the range of usually from0.1 to 10 g, and preferably from 0.3 to 5 g. By adjusting to from 0.1 to10 g, the reinforcing fiber bundle is dispersed in water (dispersionliquid) efficiently and a slurry with uniform dispersion can be obtainedin a short time. When dispersing the reinforcing fiber bundle in thewater (dispersion liquid), stirring may be conducted, if necessary.

The slurry means a suspension in which solid particles have beendispersed. The solid concentration in the slurry (i.e., the mass contentof the reinforcing fibers in the slurry) is preferably from 0.01 to 1%by mass and more preferably from 0.03 to 0.5% by mass. Because of thefact that it is from 0.01 to 1% by mass, processing by papermaking canbe conducted efficiently.

The processing of the slurry by papermaking can be performed byaspirating water from the slurry. The processing of the slurry bypapermaking can be performed following a so-called papermaking process.In an explanation by way of an example, the processing can be performedby pouring a slurry into a vessel having in its bottom a papermakingsurface through which water can be aspirated and then aspirating water.One example of the vessel is No. 2553-I (commercial name) manufacturedby Kumagai Riki Kogyo Co., Ltd., which is a vessel equipped in itsbottom with a mesh conveyor having a papermaking surface of 200 mm inwidth. Thus, a reinforcing fiber base material is obtained.

The water content of the reinforcing fiber base material to be obtainedafter dispersion is preferably adjusted to 10% by mass or less, morepreferably to 5% by mass or less before providing a binder in the step(II), i.e., the step of providing a binder. Because of this, the timerequired for the step (II) can be shortened and a prepreg can beobtained in a short time.

When the step (I) is performed by the dry process, a reinforcing fiberbase material can be obtained by dispersing a reinforcing fiber bundlein a gaseous phase. That is, a reinforcing fiber base material can beobtained by dispersing a reinforcing fiber bundle in a gaseous phase andaccumulating the reinforcing fiber bundle after the dispersion.

The dispersion of the reinforcing fiber bundle in the gaseous phaseincludes three methods, i.e., a method that is performed by opening thereinforcing fiber bundle by a non-contact system and accumulating theopened reinforcing fiber bundle (a non-contact method), a method that isperformed by opening the reinforcing fiber bundle by applying an airflow thereto and accumulating the opened reinforcing fiber bundle (amethod of using an air flow), and a method that is performed by openingthe reinforcing fiber bundle by a contact system and accumulating theopened reinforcing fiber bundle (a contact method).

The non-contact method is a method of opening a reinforcing fiber bundlewithout failing to bring it into contact with a solid or an openingmachine. For example, a method of spraying gas, such as air and inertgas, to a reinforcing fiber bundle, especially a method of pressurizingand spraying the air, which is advantageous in the cost aspect ispreferably used.

In the method of using an air flow, the conditions for applying the airflow to the reinforcing fiber bundle are not particularly restricted. Inone example, compressed air (air flow capable of applying a pressure ofnormally from 0.1 to 10 MPa, preferably from 0.5 to 5 MPa) is applieduntil the reinforcing fiber bundle is opened. In the method of using anair flow, the apparatus that can be used is not particularly restricted,and a container that is equipped with an air tube, is capable of suckingthe air, and can contain a reinforcing fiber bundle can be provided asan example. By the use of such a container, the opening and theaccumulation of a reinforcing fiber bundle can be performed in onecontainer.

The contact method is a method in which a solid or an opening machine isbrought into physical contact with a reinforcing fiber bundle to openit. Examples of the contact method include carding, needle punching, androller opening. Among these, the use of carding or needle punching ispreferred, and the use of carding is more preferred. The conditions forpracticing the contact method are not particularly restricted andconditions under which a reinforcing fiber bundle is successfully openedmay be determined appropriately.

The proportion accounted for by the reinforcing fibers in thereinforcing fiber base material is from 80 to 100% by mass, and morepreferably from 90 to 100% by mass. Because of the fact that it is from80 to 100% by mass, the reinforcing effect can be demonstratedefficiently when using a reinforcing fiber base material and hybridizingit with a matrix resin.

The basis weight of the reinforcing fiber base material is preferablyfrom 10 to 500 g/m², and more preferably from 50 to 300 g/m². If it isless than 10 g/m², troubles in handleability, such as rupture of a base,may occur, whereas if it exceeds 500 g/m², a long time may be taken fordrying a base in the wet process or a web may be thick in the dryprocess, so that it may become difficult to handle the base in thefollowing process.

In the step (II), a binder is provided to the reinforcing fiber basematerial to be obtained in the step (I).

The binder means a binder which intervenes between a reinforcing fiberbase material and a matrix resin to connect them. The binder is usuallya thermoplastic resin. Examples of the thermoplastic resin includeacrylic polymers, vinyl polymers, polyurethanes, polyamides, andpolyesters. In the present invention, one or two or more selected fromamong these examples are preferably used. Moreover, the thermoplasticresin preferably has at least one kind of functional group selected fromamong an amino group, an epoxy group, a carboxyl group, an oxazolinegroup, a carboxylic acid base group, and an acid anhydride group and itmay have two or more kinds of functional groups. Particularly, athermoplastic resin having an amino group is more preferred.

The provision of the binder to the reinforcing fiber base material ispreferably conducted in the form of an aqueous solution, an emulsion, ora suspension of the binder (for example, the aforementionedthermoplastic resin). The aqueous solution means a solution in a stateof having been dissolved in water almost completely, an emulsion means asolution (emulsion) in a state where two liquids which do not dissolvecompletely have formed fine particles in a liquid, and the suspensionmeans a solution (suspension) in a state of having been suspended inwater. The size of the component particle diameter in the liquid is inthe order, aqueous solution<emulsion<suspension. Although the system ofimpartation is not particularly restricted, a system in which a carbonfiber base is immersed in an aqueous solution, an emulsion or asuspension of a thermoplastic resin, a shower system, and so on areavailable, for example. After the contact, it is preferable to removeexcessive binder before the drying step, for example, by aspirating itor forcing is to be absorbed by an absorber, such as absorbent paper.

In the aforementioned step (II), the reinforcing fiber base material ispreferably heated after the impartation of the binder. Thereby, the timerequired for the step (III) can be shortened and a prepreg can beobtained in a short time. As to the heating temperature, the temperatureat which the reinforcing fiber base material after the impartation ofthe binder is dried can determined appropriately and it is preferablyfrom 100 to 300° C., and more preferably from 120 to 250° C.

In the step (III), a binder-imparted reinforcing fiber base material tobe obtained in the step (II) is impregnated with a matrix resin, so thatthe reinforcing fiber base material and the matrix resin are hybridizedtogether.

The hybridization of the matrix resin to the binder-imparted reinforcingfiber base material can be performed by bringing the matrix resin intocontact with the reinforcing fiber base material. Although the matrixresin in this case is not particularly restricted with respect to itsform, when the matrix resin is, for example, a thermoplastic resin, itis preferably in at least one form selected from among fabric, non-wovenfabric and film, and it is preferable that the matrix resin be in theform of non-woven fabric. The system of contact is not particularlyrestricted, and an example thereof is a method in which two sheets offabric, non-woven fabric or film of the matrix resin are prepared andthey are disposed on both sides of a binder-imparted reinforcing fiberbase material.

The hybridization is preferably performed by pressurization and/orheating, and it is more preferable that both pressurization and heatingbe carried out simultaneously. The condition of the pressurization ispreferably from 0.01 to 10 MPa, and more preferably from 0.05 to 5 MPa.The condition of heating is preferably a temperature at which the matrixresin to be used can melt and flow, and the temperature range ispreferably from 50 to 400° C. and more preferably from 80 to 350° C.Pressurization and/or heating can be performed while the matrix resin iskept in contact with the reinforcing fiber base material having beenprovided with the binder. An example is a method in which two sheets offabric, non-woven fabric, or film of the matrix resin are prepared,followed by disposing them on both sides of the binder-impartedreinforcing fiber base material and then applying heating and/or heatingfrom both sides (e.g., a method of sandwiching with a double-beltpressing machine).

A prepreg is obtained by the step (III).

In the present invention, the step (IV) may further be possessed inaddition to the aforementioned steps (I) to (III). The step (IV) is astep of hauling the prepreg obtained by the aforementioned step (III).The hauling of a prepreg can be conducted by winding it into a roll. Thehauling rate is preferably 10 m/min or more. The upper limit of thehauling rate is usually 100 m/min or less.

Among the steps (I) to (III), and the step (IV) which is carried out ifnecessary, the steps (I) and (II) are preferably carried out online.Moreover, it is more preferable that all the steps (I) to (III) and thestep (IV) which is carried out if necessary be performed online. Onlineis a system in which the respective steps are performed continuously andit is an antonym of offline. That is, online means a process in whichthe respective steps are carried out as a series of procedures anddiffers from a process in which the respective steps are independent. Byperforming the steps (I) and (II) online, it is possible to obtain aprepreg in a short time.

As to the blended amounts of the reinforcing fiber bundle, the binderand the matrix resin to the whole prepreg, that of the reinforcing fiberbundle is preferably from 10 to 80% by mass, that of the binder is from0.1 to 10% by mass, and that of the matrix resin is from 10 to 80% bymass. The adjustment to these ranges makes it easy to obtain a moldingbase that can efficiently demonstrate the reinforcement by reinforcingfibers. More preferably, that of the reinforcing fiber bundle is from 10to 60% by mass, that of the binder is from 0.5 to 10% by mass, and thatof the matrix resin is from 30 to 80% by mass. Even more preferably,that of the reinforcing fiber bundle is from 20 to 60% by mass, that ofthe binder is from 1 to 8% by mass, and that of the matrix resin is from32 to 79% by mass.

[Method for Manufacturing a Reinforcing Fiber Base Material by a WetProcess]

In the step (I) in which the aforementioned reinforcing fiber bundle isdispersed to obtain a reinforcing fiber base material, it is preferableto obtain a reinforcing fiber base material by a wet process.Particularly, it is preferable to obtain a reinforcing fiber basematerial by the following steps (i) to (iv). That is, the method is amethod for manufacturing a reinforcing fiber base material, the methodcomprising step (i) of charging a reinforcing fiber bundle to adispersion medium, step (ii) of preparing a slurry in which reinforcingfibers forming the reinforcing fiber bundle are dispersed in thedispersion medium, step (iii) of transporting the slurry, and step (iv)of removing the dispersion medium from the slurry to produce apapermaking base material containing reinforcing fibers.

In the step (i), a reinforcing fiber bundle is charged into a dispersionmedium.

The dispersion medium (dispersion liquid) means a medium that candisperse a reinforcing fiber bundle. Examples of the dispersion mediuminclude so-called solvents, such as water and alcohol, and water ispreferred. As the water, waters such as normal tap water, distilledwater and purified water, can be used. If necessary, a surfactant may bemixed with water. Although the surfactant is classified into a cationictype, an anionic type, a nonionic type, and an amphoteric type, anonionic surfactant is used preferably among them, and particularlypolyoxyethylene lauryl ether is used more preferably. The concentrationof the surfactant to be used when the surfactant is mixed with water isusually from 0.0001 to 0.1% by mass, and preferably from 0.0005 to 0.05%by mass. The viscosity of the dispersion medium can be adjusted by, ifnecessary, dissolving a macromolecular compound in the dispersionmedium. As the macromolecular compound, a water-soluble macromolecule oran organic-soluble macromolecule can be used suitably according to thekind of a solvent. When the dispersion medium is water, starch,polyvinyl alcohol, and polyethylene oxide are used more preferably. Whena macromolecular compound is dissolved in a dispersion medium, theconcentration of the macromolecular compound is preferably from 0.01 to5% by mass, and more preferably from 0.05 to 1% by mass.

As each of the solvent, the surfactant, and the macromolecular compoundwhich constitute the dispersion medium, one kind of substance may beused or alternatively two or more kinds of substances may be used.

As to the dispersion medium, its viscosity measured by using a B typeviscometer is preferably from 2 to 100 mPa·s, more preferably from 2 to80 mPa·s, and even more preferably from 3 to 50 mPa·s. When theviscosity is 1 mPa·s or more, it is possible to inhibit thereflocculation of reinforcing fibers and obtain a fiber reinforced basewith superior dispersibility. When the surface oxygen concentrationratio is 100 mPa·s or less, adhesion of the surfactant or macromolecularcompound contained in the dispersion medium will decrease and strongadhesion to a thermoplastic resin composition can be obtained.

In the step (ii) is prepare a slurry in which reinforcing fibers whichconstitute a reinforcing fiber bundle have been dispersed in adispersion medium. In the present invention, an aqueous slurry ispreferred.

The step (ii) is usually carried out in a dispersion vessel. Thedispersion vessel is a vessel (container) that can contain a slurry.When using a dispersion vessel, it is preferable to charge thedispersion medium and the reinforcing fiber bundle in the step (i)directly to the dispersion vessel. Of course, it is also permissible tocharge the dispersion medium and the reinforcing fiber bundle to avessel other than the dispersion vessel in advance and then transfer thecontent of the vessel to the dispersion vessel and carry out the step(ii). When dispersing the reinforcing fiber bender in the dispersionmedium (dispersion liquid), stirring may be conducted, if necessary.That is, the dispersion vessel may be one provided with a stirringdevice, if necessary.

In the step (iii), the slurry to be obtained in the step (ii) istransported.

The step (iii) is usually performed in the transport portion thatconnects the dispersion vessel where the step (ii) is performed to thepapermaking vessel where the step (iv) is performed.

Although the width of the transport portion is not particularly limited,it is preferred that the ratio of the width W1 of the transport portionto the width W2 of the reinforcing fiber base material, W1/W2, be 0.5 to1.0, and more preferably 0.7 to 1.0. If W1/W2 is less than 0.5, a longtime may be needed for the transportation in the step (iii) or thedispersion state may become insufficient because when a slurry flowsfrom the transport portion to the step (iv), the width of a slurry flowportion becomes large and therefore a load is applied to the slurry. IfW1/W2 exceeds 1.0, the dispersion state of the slurry in the step (iv)may become insufficient. The “width of a transport portion” as referredto herein means the major axis of the section of the transport portion;for example, when the section of a transport portion is a rectangle, itmeans the length of the longer sides. The “width of a reinforcing fiberbase material” means the width, which is shorter than the length, amongthe length the width, and the thickness of a reinforcing fiber basematerial to be used in the step (iv). If the width varies from site tosite, it means the average thereof.

The width of the transport portion usually falls within the range offrom 0.1 to 2 m. The width of the reinforcing fiber base material isusually from 0.2 to 2 m.

The shape of the transport portion is not particularly limited if it isa shape such that a slurry can be transported and usually is a tubularshape. According to need, the transport portion may be provided with aliquid transfer pump in the middle thereof. The liquid transfer pump ispreferably a low shear pump, such as a diaphragm pump and a snake pump.

The step (iii) may be a step that is performed by an overflow system.This can prevent the reinforcing fibers in a slurry to be transportedfrom sedimenting or agglomerating through the application of shearingforce to the reinforcing fibers, so that the dispersibility in slurrycan be maintained. Moreover, the transportation can be achievedeconomically without using power, such as a pump.

The overflow system means a system to send a liquid overflowing from avessel (tub) to a next vessel (tub) by using the force of gravity. Thatis, it is a system to send a liquid substantially without using power,such as a liquid transfer pump.

In using the overflow system, it is preferable that the transportportion incline. That is, in viewing the transport portion horizontally,it is preferable that the joint between the dispersion vessel and thetransport portion be located at a position that is higher than the jointbetween the papermaking vessel and the transport portion. Theinclination angle is preferably from 30 to 60° and more preferably from40 to 55°. If the inclination angle is smaller than 30°, thetransportation in the step (iii) may take a long time. If theinclination angle exceeds 60°, the flow rate of a slurry in itstransportation becomes high in the use of the overflow system, andtherefore an excessive shear will be applied to the slurry at itsarrival at the step (iv), so that the state of dispersion of the slurryin the step (iv) may become insufficient.

The inclination angle referred to herein means the degree of an anglelocated on the vertically downward side of a point where the center lineof the tube of the transport portion intersects a line that is parallelto the gravity direction.

When the step (iii) is performed in the overflow system, the joint ofthe transport portion with the dispersion vessel is preferably locatedon the wall of the dispersion vessel, particularly in its upper part.

In the use of the overflow system, it is preferable that the transportportion be in a straight shape, in other words, it be in a shape havingno direction turning point such as a curved portion or a bent portion inthe middle.

In the use of the overflow system, the height of the transport portionis preferably 60 mm or more, and more preferably 100 mm or more. Becauseof the fact that it is 60 mm or more, it is possible to render thecontact area of the wall of the transport portion with the slurryrelatively small for the amount of the slurry to be transported and itis possible to reduce reflocculation of dispersed fibers due to thegeneration of shear force to the slurry at the time of contact with thewall. The height of a transport portion referred to herein means thelength of the diameter of the transport portion when viewing thetransport portion horizontally. When the transport portion is arectangle (the longer sides are in the base width direction and theshorter sides are in the base thickness direction), the length of theshorter sides corresponds to the “height of the transport portion.” Theupper limit of the height of the transport portion is not particularlylimited and it is usually 500 mm or less. If the height of the transportportion differs position by position, it shall mean the average.

The shape of the transport portion is explained by taking FIG. 13 toFIG. 20 as examples. FIG. 13 to FIG. 20 are drawings that schematicallyillustrate the horizontally viewed locational relationship between thedispersion vessel, the papermaking vessel, and the transport portion ina case where the steps (i) and (ii) are carried out in the dispersionvessel, the step (iv) is performed in the papermaking vessel, and thestep (iii) is carried out in the transport portion connecting thedispersion vessel with the papermaking vessel. The transport portion 213depicted in each of FIG. 13 to FIG. 18 and FIG. 20 is straight.

The inclination angle of the transport portion means an angle r which isformed vertically downward by the central line q of the transportportion 213 and the line p that extends in the direction gravity in eachdiagram. The transport portion 213 in each of FIG. 13, FIG. 17 and FIG.18 inclines from the dispersion vessel 211 towards the papermakingvessel 212 and the inclination angle thereof is from 30 to 60°. Thetransport portion 213 in FIG. 14 connects the dispersion vessel 211 andthe papermaking vessel 212 horizontally and the inclination anglethereof is about 90°. The transport portion 213 in FIG. 15 inclines fromthe dispersion vessel 211 towards the papermaking vessel 212 and theinclination angle thereof is from 30 to 60°. The transport portion 213in FIG. 16 connects the dispersion vessel 211 and the papermaking vessel212 vertically and the inclination angle thereof is about 0°. Thetransport portion 213 in FIG. 20 also has an inclination angle of about0° like that in FIG. 16, and a pump 225 is mounted in the middle of thetransport portion 213.

In FIG. 13, FIG. 17, and FIG. 18, the connecting part 214 of thetransport portion 213 to the dispersion vessel 211 is located at anupper part of the wall of the dispersion vessel 211. Therefore, apositional relationship of a dispersion vessel, a papermaking vessel anda transport portion like that illustrated in FIG. 13 makes it possibleto perform the step (iii) in an overflow system.

In the step (iv), a papermaking base material containing reinforcingfibers, that is, a reinforcing fiber base material is obtained byremoving the dispersion medium from the slurry.

The step (iv) is usually carried out in a papermaking vessel. Thepapermaking vessel is a vessel (container) that can contain a slurry andhas a papermaking surface through which moisture can be aspirated. Thepapermaking surface is generally provided near the bottom and examplesof the material thereof include a mesh sheet.

In the present invention, the reinforcing fiber base material to beobtained in the step (iv) can be hauled. The hauling of a reinforcingfiber base material can be conducted by winding the reinforcing fiberbase material into a roll. The hauling rate is preferably 10 m/min ormore. The upper limit of the hauling rate is usually 100 m/min or less.

It is preferable that the steps (i) to (iv) be performed online.

It is preferable that the level H1 of the surface of the slurry in thestep (ii) be at a position that is higher than the level H2 of thesurface of the slurry in the step (iv). The “level of the surface of aslurry” means the position of the surface in viewing the slurryhorizontally. “To be at a position that is higher” means that when thelevels of the two surfaces are each expressed by a measured value of adistance from a standard that is located vertically below the level, onelevel is located at a higher position than the other, in other words,one of the levels of the two surfaces is located vertically below theother.

In particular, it is preferable that the difference H1−H2 between thelevel H1 of the surface of the slurry in the step (ii) and the level H2of the surface of the slurry in the step (iv) be from 0.1 to 5 m, morepreferably from 0.5 to 2 m. If it is less than 0.1 m, the transportationin the step (iii) may require a long time. On the other hand, if itexceeds 5 m, the state of dispersion of the slurry in the step (iv) maybecome insufficient.

The level H1 of the surface of the slurry in the step (ii) and the levelH2 of the surface of the slurry in the step (iv) are explained on thebasis of FIG. 13 to FIG. 20. The level H1 of the surface of the slurry(shadow area) in the dispersion vessel 211 is represented by thedistance H1 of position B of a surface relative to a standard A locatedvertically below H1 and H2. The level H2 of the surface of the slurry(shadow area) in the papermaking vessel 212 is represented by thedistance H2 of position C of a surface relative to a surface standard A.In order to maintain the difference between the levels H1 and H2 of thesurfaces of the slurries, it is preferable that the dispersion vessel211 and the papermaking vessel 212 be positioned with a gap in thegravity direction as illustrated in FIG. 13, FIG. 15, FIG. 16, and FIG.19, but it is also permissible that the positions of the dispersionvessel 211 and the papermaking vessel 212 in the gravity direction maybe level if the levels of the surfaces of the slurries in the respectivevessels are adjusted by the amounts of the slurries and the size of thevessels as illustrated in FIG. 14, FIG. 17, and FIG. 18.

In order to maintain the level H1 of the surface of the slurry in thestep (ii) at a position higher than the level H2 of the surface of theslurry in the step (iv), it is preferable that, for example, when thestep (ii) is performed in the dispersion vessel and the step (iv) isperformed in the papermaking vessel, these two vessels be mounted sothat the position of the bottom of the dispersion vessel may be locatedvertically above the position of the top of the papermaking vessel.

It is preferable that the time taken from the step (i) to the start ofthe step (iv) be up to 10 minutes. If it exceeds 10 minutes, thereinforcing fibers dispersed in the slurry may reflocculate according tothe kind of the reinforcing fibers. The lower limit of the time to betaken from the step (i) to the start of the step (iv), which is notparticularly limited, is usually one minute or more.

It is preferable that a dispersion medium and a reinforcing fiber bundlebe charged continuously in the step (i) and the steps (i) to (iv) beexecuted continuously. Thereby, a reinforcing fiber base material can beobtained in a shorter time. If a large amount of slurry is charged inone portion, a long time may be taken before part of the slurry isprocessed and, as a result, the dispersion state may become defective;however, continuous charging and execution makes it possible to performpapermaking a slurry little by little efficiently while maintaining thedispersion state. “To charge continuously” and “to execute continuously”mean to charge continuously and to execute the steps (ii) to (iv) forthe raw materials charged in the step (i) one after another orcontinuously. In other words, they mean a state that the charging of theraw materials of a dispersed slurry and the charging of the slurry areexecuted continuously in a series of steps and mean a process with moreconsideration for mass manufacture than a process in which a certainamount of slurry is produced first. Examples of the methods for thecontinuous charging or execution include methods of other than a batchsystem, a method of charging at a fixed rate, and a method of chargingin almost equal portions at prescribed intervals. One example of theconditions for charging at a fixed rate is such a condition that adispersion medium is charged at a rate of from 1×10³ to 1×10⁷ g/min anda reinforcing fiber bundle at a rate of from 0.1 to 1×10⁵ g/min. Oneexample of the conditions for charging in almost equal portions inprescribed intervals is such a condition that a dispersion medium ischarged at every 1 to 5 minutes in an amount of from 1×10³ to 1×10⁷ gand a reinforcing fiber bundle at every 1 to 5 minutes in an amount offrom 0.1 to 1×10⁵ g.

The level H1 of the surface of the slurry in the step (ii) is preferablykept at substantially the same level throughout the step (ii).Especially when the steps (i) to (iv) are executed continuously, thelevel H1 of the surface of the slurry in the step (ii) is preferablykept at substantially the same level throughout the step (ii).

“To be kept at substantially the same level throughout the step (ii)”means that the variation of the level during the execution of the step(ii) is within 100 mm, preferably within 50 mm, and more preferably novariation (0 mm). In order to keep the level H1 of the surface of theslurry in the step (ii) at substantially the same level throughout thestep (ii), it is preferable to execute the step (i) continuously. Forexample, when performing step (ii) in the dispersion vessel, it ispreferable to perform the charging of the dispersion medium and thereinforcing fibers to the dispersion vessel continuously and perform thesteps (i) to (iv) continuously.

Moreover, in the method for manufacturing a reinforcing fiber basematerial by a wet process in the present invention, any of the followingmanufacture methods a, b, and c or a combination of these is preferred.

[Evaluation of the Method a for Manufacturing a Reinforcing Fiber BaseMaterial by a Wet Process]

In methods for manufacturing a papermaking-processed body in which asolid component has been mixed uniformly, it has been proposed to dilutea slurry concentration before charging a raw material slurry to apapermaking step (JP 2006-104608 A). Specifically, it has been proposedto prepare a slurry with a high reinforcing fiber concentration and thendiluting this to produce a slurry with a low reinforcing fiberconcentration in order to keep the dispersibility of reinforcing fibersin a slurry. However, there is a problem that the work becomes morecomplicated due to the execution of two stages and, in the case ofreinforcing fibers which are low in affinity to the dispersion medium ofa slurry, it is very difficult to produce a slurry with a highreinforcing fiber concentration.

Then, in the method for manufacturing a reinforcing fiber base materialby a wet process in the present invention, it is preferable to producethe product by the following method. That is, the method is a method formanufacturing a reinforcing fiber base material, the method comprisingstep (i-a) of charging a reinforcing fiber bundle to a dispersionmedium, step (ii-a) of preparing a slurry in which reinforcing fibersforming the reinforcing fiber bundle are dispersed in the dispersionmedium, step (iii-a) of transporting the slurry, and step (iv-a) ofremoving the dispersion medium from the slurry to produce a papermakingbase material containing reinforcing fibers, wherein C1/C2 is within arange of from 0.8 to 1.2 where the mass content of the reinforcingfibers in the slurry to be prepared in the step (ii-a) is expressed byC1 and the mass content of the reinforcing fibers in the slurry at thetime of the commencement of the step (iv-a) is expressed by C2.According to this method for manufacturing a reinforcing fiber basematerial, the method can be applied to reinforcing fibers with lowaffinity to a dispersion medium in slurry preparation and can keep fiberdispersibility of reinforcing fibers in papermaking, and it is possibleto obtain, in a short time, a reinforcing fiber base material which willafford a molded product superior in mechanical properties if beingprocessed into a molded product with incorporation of a resin or thelike. Henceforth, this method for manufacturing a reinforcing fiber basematerial is referred to as manufacturing method a.

In manufacture method a, C1/C2 is adjusted to within a range of from 0.8to 1.2 where the mass content of the reinforcing fibers in the slurry tobe prepared in the step (ii-a) is expressed by C1 and the mass contentof the reinforcing fibers in the slurry at the time of the commencementof the step (iv-a) is expressed by C2. C1/C2 is preferably within arange of from 0.9 to 1.1. If C1/C2 is less than 0.8, it is necessary toremove only the dispersion medium or add only reinforcing fibers inorder to increase C2, the process becomes complicated, and thedispersion state of the slurry may become insufficient. If C1/C2 exceeds1.2, the dispersion state of the slurry in the step (iv-a) may becomeinsufficient.

The time to be taken by the step (ii-a) is preferably up to 10 minutes,more preferably up to 5 minutes, and even more preferably up to 3minutes. If it exceeds 10 minutes, the reinforcing fibers dispersed inthe slurry may reflocculate according to the kind of the reinforcingfibers. The lower limit of the time to be taken by the step (ii-a),which is not particularly limited, is usually one minute or more.

The rate of charging of a slurry in the step (iii-a), that is, the flowrate of a slurry to the step (iv-a) is preferably from 0.001 to 0.1m³/sec, and more preferably from 0.005 to 0.05 m³/sec. If it is lessthan 0.001 m³/sec, the charging rate is small and a long time will berequired for a process, so that the manufacture efficiency may lower;whereas if it exceeds 0.1 m³/sec, shear is prone to be applied to aslurry because of a high flow rate of the slurry and therefore thedispersion state may become insufficient.

In the steps (ii-a) to (iv-a), it is preferable to perform papermakingwhile adjusting a fiber concentration parameter nL³ to within a range of(0<) nL³<L/D. Here, the respective parameters are as follows.

n: The number of the reinforcing fibers contained per unit volume of aslurryL: Length of a reinforcing fiberD: Diameter of a reinforcing fiber.

A schematic diagram of a slurry containing reinforcing fibers is shownin FIG. 30. Doi, M. and Edwards, S. F., The Theory of Polymer Dynamics324 (1986) discloses that a rarefied state is produced when the fiberconcentration parameter nL³ satisfies nL³<1 and a quasi-rarefied stateis produced when 1<nL³<L/D. That the fiber concentration parameter nL³is less than L/D is preferred for inhibiting reflocculation ofreinforcing fibers and increasing the dispersibility of reinforcingfibers in a slurry because if so, the reinforcing fibers dispersed inthe slurry become difficult to dynamically interfere with each other. Itis preferable that the concentration of reinforcing fibers be as low aspossible because the lower the concentration, the more thedispersibility of the reinforcing fibers can be increased. However, whenwishing to secure the basis weight or the thickness of a reinforcingfiber base material to be obtained or when wishing to increase themanufacture efficiency of a reinforcing fiber base material, it ispreferable to increase the concentration of the reinforcing fibers andit is preferable to perform papermaking at a reinforcing fiberconcentration of 1<nL³<L/D, which is a quasi-rarefied state.

[Evaluation of the Method b for Manufacturing a Reinforcing Fiber BaseMaterial by a Wet Process]

It has been disclosed that a wet-system method for manufacturing afiber-reinforced thermoplastic resin sheet includes controlling thestructure in a headbox through which a dispersion liquid passes and thecondition to be used in charging the dispersion liquid onto a mesh beltfrom the headbox (JP 8-232187 A and JP 9-136969 A). It has beendisclosed that it is thereby possible to obtain a fiber-reinforcedthermoplastic resin sheet without local unevenness with respect to basisweight or without abnormal orientation of reinforcing fibers and that itis possible to obtain a fiber-reinforced thermoplastic resin sheet withno variation of basis weight distribution in the width direction.

However, the methods of JP 8-232187 A and JP 9-136969 A is required touse a liquid transfer pump as power for transporting a slurry.Therefore, shear is prone to occur, so that it was difficult to maintaina dispersion state for a long time.

Then, in the method for manufacturing a reinforcing fiber base materialby a wet process in the present invention, it is preferable also toproduce the product by the following method. That is, the method is amethod for manufacturing a reinforcing fiber base material, the methodcomprising step (i-b) of charging a reinforcing fiber bundle to adispersion medium, step (ii-b) of preparing a slurry in whichreinforcing fibers forming the reinforcing fiber bundle are dispersed inthe dispersion medium, step (iii-b) of transporting the slurry, and step(iv-b) of removing the dispersion medium from the slurry to produce apapermaking base material containing reinforcing fibers, wherein thesteps (i-b) to (iv-b) are carried out online and the level H1 of thesurface of the slurry in the step (ii-b) is higher than the level H2 ofthe surface of the slurry in the step (iv-b). According to this methodfor manufacturing of a reinforcing fiber base material, it is notnecessary to use a liquid transfer pump as power for transporting aslurry in the step (iii-b). Therefore, shear of a slurry becomes harderto occur and a dispersion state can be kept for a long time. Moreover,flocculation of fibers is inhibited and it is possible to obtain, in ashort time, a reinforcing fiber base material which will afford a moldedproduct superior in mechanical properties if being processed into amolded product with incorporation of a thermoplastic resin. Henceforth,this method for manufacturing a reinforcing fiber base material isreferred to as manufacturing method b.

In manufacture method b, the level H1 of the surface of the slurry inthe step (ii-b) is rendered higher than the level H2 of the surface ofthe slurry in the step (iv-b). Rendering H1 higher than H2 eliminatesthe necessity of using a liquid transfer pump in order to transfer theslurry in the step (iii-b). That is, it is not necessary to install aliquid transfer pump in a transport portion as shown in FIG. 308.

[Evaluation of the Method c for Manufacturing a Reinforcing Fiber BaseMaterial by a Wet Process]

In the methods of JP 8-232187 A and JP 9-136969 A, it is necessary touse a liquid transfer pump as power for transporting a slurry containingreinforcing fibers and a thermoplastic resin when transporting theslurry and there was a problem that reinforcing fibers dispersed once ina dispersion vessel reflocculated due to a turbulent flow generated inthe liquid transfer pump part and, as a result, the dispersion state ofthe reinforcing fibers in a papermaking base material got worse.

Moreover, in the methods of JP 8-232187 A and JP 9-136969 A, since aslurry containing reinforcing fibers and a thermoplastic resin istransported using a transport portion with a branched structure as apassage when transporting the slurry to a papermaking vessel, there wasa problem that a turbulent flow was generated at a branch point of thebranched structure and reinforcing fibers dispersed once in a dispersionliquid reflocculated, so that the dispersion state of the reinforcingfibers in a papermaking base material got worse.

Then, in the method for manufacturing a reinforcing fiber base materialby a wet process in the present invention, it is preferable also toproduce the product by the following method. That is, the method is amethod for manufacturing a reinforcing fiber base material, the methodcomprising step (i-c) of charging a reinforcing fiber bundle to adispersion medium, step (ii-c) of preparing a slurry in whichreinforcing fibers forming the reinforcing fiber bundle are dispersed inthe dispersion medium, step (iii-c) of transporting the slurry, and step(iv-c) of removing the dispersion medium from the slurry to produce apapermaking base material containing reinforcing fibers, wherein thesteps (i-c) and (ii-c) are carried out in a dispersion vessel, the step(iv-c) is carried out in a papermaking vessel, the step (iii-c) iscarried out in a transport portion that connects the dispersion vesseland the papermaking vessel, and the slurry is transported in a laminarflow state or in a transition region state from a laminar flow to aturbulent flow in the transport portion. According to this method formanufacturing a reinforcing fiber base material, by transporting aslurry in a laminar flow state or in a state of a transition region froma laminar flow to a turbulent flow, in a prescribed step of themanufacture process, reflocculation of reinforcing fibers is inhibitedand a fiber-reinforced base with a superior dispersion state can beobtained. Henceforth, this method for manufacturing a reinforcing fiberbase material is referred to as manufacturing method c.

In manufacture method c, in a transport portion of the step (iii-c), aslurry is transported in a laminar flow state or in a state of atransition region from a laminar flow to a turbulent flow. The laminarflow is a state that the slurry flowing in a transport portion flows inparallel with the tube axis of the passage of the transport portion. Theturbulent flow is a state that the slurry flowing in a transport portionforms whirlpools of various sizes irregularly in the transport portion.The transition region from a laminar flow to a turbulent flow is a statethat a laminar flow state and a turbulent flow state of the slurryflowing in a transport portion are mixed in the transport portion. Ifthe slurry is transported in a laminar flow state or in a state of atransition region from a laminar flow to a turbulent flow in thetransport portion, it is possible to transport a slurry that containsdispersed reinforcing fibers and that was obtained in a dispersionvessel to a papermaking vessel while maintaining the dispersion state ofthe reinforcing fibers, and reflocculation of the reinforcing fibers canbe inhibited, and a fiber-reinforced base with superior dispersibilitycan be obtained. From the viewpoint of inhibiting the reflocculation ofreinforcing fibers, it is preferable that a slurry be transported in alaminar flow state in a transport portion.

It is preferable that the flow rate of a slurry in the transport portionbe from 0.01 to 10 m/s. It is preferable that the flow rate of theslurry be within this range because if so, the flow rate distribution ina passage of the transport portion is small and a slurry that containsdispersed reinforcing fibers and that is obtained in a dispersion vesselcan be transported to a papermaking vessel while maintaining thedispersion state of the reinforcing fibers. The slurry flow rate of thetransport portion can be determined from the following formula using thetime T (second) taken for transporting 0.01 m³ of slurry, the amount ofthe slurry transported (0.01 m³), and the cross-sectional area S (m^(a))of the transport portion.

Slurry flow rate (m/s)=0.01/(S×T).  (Formula)

The cross-sectional shape of the transport portion, which is notparticularly restricted, is preferably a circle or a polygon (triangleto decagon) from the viewpoint of preventing reflocculation ofreinforcing fibers in the step (iii-c) of transporting the slurry to thestep (iv-c), and examples include the cross-sectional shapes illustratedin FIG. 21( a) and FIG. 21( b). The cross-sectional shape of thetransport portion also may be an open passage as illustrated in FIG. 21(c) or FIG. 21( d). Here, FIG. 21( a) through FIG. 21( d) are figuresschematically illustrating the cross-sectional shape of the transportportion. From the viewpoint of contamination of foreign substances atthe transport portion, the cross-sectional shape of the transportportion is more preferably a circle or a polygon.

From the viewpoint of preventing reflocculation of reinforcing fibers,the cross-sectional shape of the transport portion is preferably aregular shape so as not to generate a whirlpool in the passage of thetransport portion. From the viewpoint of preventing the reflocculationof reinforcing fibers, it is preferable that the transport portion have,in its middle, no direction turning point, such as a curved portion anda bent portion, where whirlpools readily occur in the tube of thetransport portion.

When the cross-sectional shape of a transport portion in the transportportion is a circular shape of a polygonal shape as illustrated in FIG.21( a) and FIG. 21( b), the Reynolds number, which indicates the stateof flow of a slurry, is preferably up to 4000, more preferably up to3000, and even more preferably up to 2000 from the viewpoint ofpreventing the reflocculation of reinforcing fibers. When thecross-sectional shape of a transport portion in the transport portion isan open passage as illustrated in FIG. 403 and FIG. 404, the Reynoldsnumber, which indicates the state of flow of a slurry, is preferably upto 500000, more preferably up to 300000, and even more preferably up to100000 from the viewpoint of preventing the reflocculation ofreinforcing fibers. Here, the Reynolds number Re in the transportportion was determined from the following formula by using a specificgravity ρ (kg/m³) of a dispersion liquid, the maximum length L (m) ofthe cross-section of the transport portion, the slurry flow rate (m/s)at the transport portion, and the viscosity η (Pa·s) of the dispersionmedium.

Re=ρLU/η.  (Formula)

Although the method for transporting a slurry in a laminar flow state orin a state of a transition region from a laminar flow to a turbulentflow, in the transport portion is not particularly restricted, examplesthereof include a method in which a slurry is transported from adispersion vessel to a papermaking vessel via a transport portion byusing a potential energy by placing the dispersion vessel at a positionhigher than the papermaking vessel, and a method in which a slurry istransported from a dispersion vessel to a papermaking vessel via atransport portion by increasing the pressure in the dispersion vessel byinjecting gas into the dispersion vessel containing the slurry. Such atransportation method failing to use a liquid transfer pump arepreferable because they can reduce the generation of a turbulent flow inthe transport portion, can prevent the reflocculation of reinforcingfibers, and can maintain the dispersibility of a slurry.

When it is necessary to transport a large amount of slurry from adispersion vessel to a papermaking vessel while the slurry is in alaminar flow state or in a state of a transition region from a laminarflow to a turbulent flow by mounting a plurality of transport portions,it is permissible to increase the amount of the slurry to be transportedfrom the dispersion vessel to the papermaking vessel by mounting aplurality of transport portions.

[Preform]

The preform of the present invention is a preform that contains, as alamination unit, a prepreg in which at least a reinforcing fiber basematerial has been impregnated with a thermoplastic resin, wherein theprepreg has an average of two-dimensional orientation angles each formedby a reinforcing filament (a) contained in the prepreg and a reinforcingfilament (b) that intersects the reinforcing filament (a) of from 10 to80°, a thickness h0 (mm) at 23° C. of 0.03 to 1 mm, and a tensilestrength σ of 0.01 MPa or more.

These constituents are explained below.

The preform of the present invention comprises at least two moldingmaterials having been laminated and is to be subjected to a molding stepdirectly or via a secondary processing step, and it means a state beforebeing processed into a molded product. The secondary processing step isnot particularly restricted, and examples thereof include a cutting stepof cutting a preform into a prescribed size or shape, a bonding step ofimproving the handling performance of a preform by adhering prepregstogether, a degassing step of removing air from a preform, and a surfacetreatment step of activating a preform by plasma treatment or the like.

It is important to use a prepreg in which at least a reinforcing fiberbase material has been impregnated with a resin for the preform of thepresent invention from the viewpoint of the lightness and the mechanicalproperties of a molded product to be obtained. Moreover, from theviewpoint of the handling performance of a preform, it is important thatthe average of two-dimensional orientation angles each formed by areinforcing filament (a) contained in the prepreg and a reinforcingfilament (b) that intersects the reinforcing filament (a) is from 10 to80°. Here, as to the two-dimensional orientation angle, the definitionused in the explanation of the aforementioned prepreg can be applied. Ifthe average of two-dimensional orientation angles is smaller than 10°,unidirectional reinforcing fibers or the like have no resistance to astress of a direction that is perpendicular to the fiber longitudinaldirection and a preform may rupture during a process of conveying ormolding the preform at a high speed. If the average of two-dimensionalorientation angles exceeds 80°, since reinforcing fibers stretch in twodirections in a bidirectional reinforcing fiber fabric or the like,sufficient stretchability may not be obtained in a molding step and,therefore, molding may be achieved defectively or the quality of amolded product may be impaired. Moreover, in such a unidirectionalreinforcing fiber or a bidirectional reinforcing fiber fabric, the gapbetween reinforcing fibers is small and, therefore, the penetration of aresin may become insufficient in a molding step and, as a result, themechanical properties may lower. Furthermore, that the prepreg is closerto isotropic is preferred because if so, the labor in a lamination stepwill be reduced and the preform can be processed into a preform at ahigh speed and a reduced amount of loss of materials will be generated,so that an economic burden can be reduced. The two-dimensionalorientation angle of the reinforcing fibers to be used in the presentinvention is preferably from 20 to 70°, more preferably from 30 to 60°,and it is better that the average is closer to 45°, which is the idealangle.

From the viewpoint of the handling performance of the preform of thepresent invention, it is also important that the thickness h0 (mm) of aprepreg at 23° C. be from 0.03 to 1 mm. If h0 is less than 0.03 mm, thepreform may rupture during a process of conveying or molding the preformat a high speed. If h0 exceeds 1 mm, the fiber orientation in thethickness direction becomes greater and a preform develops thicknessexpansion in a step of molding, so that the quality of a molded productmay be impaired due to deformation or conveyance to a mold may beobstructed. The thickness h0 at 23° C. of the prepreg to be used in thepresent invention is preferably from 0.05 to 0.8 mm, and preferably from0.1 to 0.6 mm.

From the viewpoint of the handling performance of the preform of thepresent invention, the tensile strength σ of the prepreg is 0.01 MPa ormore, preferably 0.1 MPa or more, and more preferably 1 MPa or more.There are no particular limitations with respect to the upper limit ofσ, but a general example thereof is 1000 MPa or less. If the tensilestrength σ is less than 0.01 MPa, problems, such as rupture of aprepreg, may occur during operations of molding.

Although there are no particular restrictions with respect to thereinforcing fibers and the resin to constitute the prepregs to be usedfor the preform of the present invention, it is preferable to use theaforementioned prepreg (henceforth, referred to as prepreg (A)) from theviewpoint of obtaining a molded product that can satisfy moldabilityinto a complicated shape and mechanical properties.

In the preform of the present invention, for the purpose of satisfyingthe specifications of a molded product to be obtained, it is preferablethat a prepreg (A) constitute a plurality of lamination units and atleast two kinds of prepregs (A) such that at least one factor among thefactors of the prepregs is substantially different be used for thepreform. Here, the respective factors of the aforementioned prepreg areexplained.

The first factor is the volume ratio of reinforcing fibers. The elasticmodulus, the strength, and the dimensional stability of a molded productto be obtained will be improved as the volume ratio of reinforcingfibers increases. On the other hand, the appearance quality of a moldedproduct tends to deteriorate as the volume ratio of reinforcing fibersincreases. Then, it is preferable, from the viewpoint of reconciling thelightness and the appearance quality of a molded product, to laminate aprepreg that is higher in reinforcing fiber proportion and a prepregthat is lower in reinforcing fiber proportion in combination. Forexample, there can be mentioned a method in which a prepreg that ishigher in reinforcing fiber proportion is laminated outside and aprepreg that is lower in reinforcing fiber proportion is laminatedinside for the purpose of increasing the rigidity of a molded product,and a method in which a prepreg that is lower in reinforcing fiberproportion is laminated further outside for the purpose of increasingthe appearance quality of a molded product. Here, that the volumeproportion of reinforcing fibers is substantially different means thatthe difference with respect to volume proportion between a prepreg thatis higher in volume proportion of reinforcing fibers and a prepreg thatis lower in volume proportion of reinforcing fibers is 5% by volume ormore.

The next factor is the length of reinforcing fibers. The elasticmodulus, the strength, and the dimensional stability of a molded productto be obtained will be improved as the length of reinforcing fibersincreases. On the other hand, the handling performance of a preform orthe appearance quality of a molded product tends to deteriorate as thelength of reinforcing fibers becomes longer. Then, it is preferable,from the viewpoint of reconciling the handling performance of a preformand the mechanical properties and the appearance quality of a moldedproduct, to laminate a prepreg that is larger in reinforcing fiberlength and a prepreg that is smaller in reinforcing fiber length incombination. For example, there can be mentioned a method in which aprepreg that is larger in reinforcing fiber length is laminated outsideand a prepreg that is smaller in reinforcing fiber length is laminatedinside for the purpose of increasing the rigidity of a molded product,and a method in which a prepreg that is smaller in reinforcing fiberlength is laminated further outside for the purpose of increasing theappearance quality of a molded product. That reinforcing fibers aresubstantially different in length means that the fiber length ratio of alonger reinforcing fiber and a shorter reinforcing fiber (the length ofa longer reinforcing fiber)/(the length of a shorter reinforcing fiber)is 1.5 or more.

The next factor is the tensile modulus of reinforcing fibers. Theelastic modulus of a molded product to be obtained increases as thetensile modulus becomes higher. On the other hand, the processability offibers deteriorates as the tensile modulus becomes higher, and, as aresult, the handling performance of a preform may deteriorate or it maybecome more disadvantageous with respect to economical efficiency. Then,it is preferable, from the viewpoint of reconciling the handlingperformance of a preform and the rigidity of a molded product, tolaminate a prepreg that is higher in tensile modulus and a prepreg thatis lower in tensile modulus in combination. For example, there can bementioned a method in which a prepreg that is higher in tensile moduluscontaining carbon fibers or the like is laminated outside and a prepregthat is lower in tensile modulus containing glass fibers or the like islaminated inside for the purpose of reconciling the rigidity of a moldedproduct and the economic efficiency, and a method in which a prepregthat uses carbon fibers higher in tensile modulus is laminated furtheroutside and a prepreg that uses carbon fibers lower in tensile modulusis laminated inside. That reinforcing fibers are substantially differentin tensile modulus means that the tensile modulus ratios of a tensilemodulus of a reinforcing fiber with a higher tensile modulus and areinforcing fiber with a lower tensile modulus (higher tensile modulusof a reinforcing fiber)/(lower tensile modulus of a reinforcing fiber)is 1.2 or more.

Next, the basis weight of a prepreg is explained. The larger the basisweight is, the thicker the prepreg tends to be and, therefore, the morethe number of lamination or the labor for the lamination can be reduced.On the other hand, the larger the basis weight is, the more thefollowability to the thickness or the shape of a molded product lowers.Then, from the viewpoint of reconciling the handling performance orshape followability of a preform with an economical efficiency, it ispreferable to laminate a prepreg with a larger basis weight and aprepreg with a smaller basis weight in combination. For the same reason,also as to the thickness of a prepreg, it is preferable to laminate aprepreg with a larger thickness h0 at 23° C. and a prepreg with asmaller h0 in combination. That the basis weight is substantiallydifferent means that the basis weight ratio of the prepreg with a basisweight and the prepreg with a smaller basis weight (i.e., (basis weightof the prepreg with a larger basis weight)/(basis weight of the prepregwith a smaller basis weight)) is 1.2 or more. That the thickness h0 at23° C. is substantially different means that the h0 ratio of the prepregwith a larger h0 and the prepreg with a smaller h0 (i.e., (h0 of theprepreg with a larger h0)/(h0 of the prepreg with a smaller h0)) is 1.2or more.

From the viewpoint of moldability, it is preferable for the preform ofthe present invention that the interlayer shear strength between aprepreg and a lamination unit adjoining the prepreg be from 0 to 50 MPa,and more preferably from 0 to 40 MPa. If the interlayer shear strengthis within a preferable range, it is possible to increase the shapabilityto an uneven form through stretching and shrinking of a preformaccompanied by interlayer shift in a molding step. The interlayer shearstrength of a preform can be measured by cutting a specimen from apreform and conducting a three-point bending test in accordance withASTM-D-2344. When the preform has been adhered partially or sealed,measurement may be done by preparing a specimen so that the adheredportion or the sealed portion may be included.

Moreover, it is preferable for the preform of the present invention thata prepreg (A) and another lamination unit (B) have been laminate for thepurpose of satisfying specifications of a molded product to be obtained.Here, a preferable embodiment of another lamination unit (B) isexplained.

First, from the viewpoint of improving the reinforcing effect of amolded product to be obtained, it is preferable that the above-mentionedlamination unit (B) be a base material containing reinforcing fibers. Inparticular, continuous reinforcing fibers are preferred from theviewpoint of increasing the impact strength of a molded product.Examples of a form including a unidirectional base material, a textilebase material, and a mat base material. On the other hand, discontinuousreinforcing fibers are preferred from the viewpoint of improving theshape followability of a molded product. Examples of a form include aunidirectional base material, i.e., a base material in which cutreinforcing fibers have been arranged in one direction, a mat basematerial, a sheet molding compound (SMC) base material, and an extrudedsheet base material.

The reinforcing fibers to constitute this lamination unit (B) are notparticularly restricted and can be selected in the same manner as thereinforcing fibers to constitute the aforementioned prepreg. Inparticular, from the viewpoint of weight reduction, carbon fibers of PANtype, pitch type, rayon type, or the like are preferably used becausethey are high in strength and specific rigidity. Moreover, from theviewpoint of increasing the handling performance of a preform, it ispreferable that the lamination unit (B) have been impregnated with athermoplastic resin or a thermosetting resin for the purpose ofmaintaining the form of the reinforcing fibers. Here, the thermoplasticresin and the thermosetting resin to be used are not particularlyrestricted and can be selected in the same manner as the thermoplasticresin and the thermosetting resin to constitute the aforementionedprepreg. There are not particular limitations with respect to theimpregnation ratio of a resin, and like the aforementioned prepreg, itis preferably from 30 to 100% for the purpose of maintaining the form ofthe reinforcing fibers.

Next, from the viewpoint of securing a prescribed thickness in a moldedproduct and keeping the thickness of a molded product uniform, asheet-form base material is preferably used as the lamination unit (B).Moreover, from the viewpoint of increasing the stretchability of apreform and increasing the followability to an uneven shape, the use ofa non-woven fabric base material is preferred. Furthermore, from theviewpoint of increasing the lightness of a molded product to beobtained, the use of a porous base material is preferred. Although thereis no particular restriction as to the material to constitute these basematerials, a thermoplastic resin to constitute the aforementionedprepreg is used more preferably from the viewpoint of processability tobase materials. Like the thermoplastic resin to constitute theaforementioned prepreg, these thermoplastic resins may, if needed,contain an alloy component, a blended material, and an additive.Moreover, from the viewpoint of improving the lightness of a moldedproduct to be obtained, the bulk density of the sheet-shaped basematerial, the nonwoven fabric base material or the porous base materialis preferably from 0.01 to 1.0, more preferably from 0.05 to 0.9, andparticularly preferably from 0.1 to 0.8.

From the viewpoint of easily performing the modification of the surfaceof a molded product to be obtained and impartation of functions, it ispreferable to dispose a film made of resin as the aforementionedlamination unit (B) on the outermost layer of the preform. As to theresin, the use of a thermoplastic resin is preferred becauseprocessability to film or adhesiveness with a preform is simple and easyand the use of a thermosetting resin is preferred because it can improvethe surface smoothness of a primer, a paint, or a gel coat. When amolded product to be obtained is used for an electronic instrument orthe like, the flame retardancy of a film is preferably equal to or morethan VTM-1, and more preferably equal to or more than VTM-0, provided inthe UL-94 standard. The method for securing the flame retardancy of afilm is not particularly restricted, and examples thereof include amethod that comprises processing a highly flame retardant resin, such asPPS, PEI, PEEK and phenol resin, into a film, a method that comprisesblending a highly flame retardant resin with a thermoplastic resin andthen processing them into a film, and a method that comprises mixing aflame retardant with a thermoplastic resin and then processing them intoa film.

Moreover, it is preferable to use, as the lamination unit (B), at leastone selected from among a decorative film, a transparent film, and acolor tone film, from the viewpoint of improving the design of a moldedproduct to be obtained. As the decorative film is preferred a filmhaving on its surface a design and/or a geometric pattern. As thetransparent film is preferred a film whose visible light transmittanceis from 80 to 100%. As the color tone film is preferred a filmcontaining an organic and/or inorganic pigment of a colorant. Inaddition, according to need, a gloss film, a print film, an antistaticfilm, a light shielding film, a heat-resistant film, and so on can beused as the lamination unit (B).

Other than the examples provided above, a metal plate, a metal foil, ametal mesh, a graphite sheet, a heat radiation sheet, a honeycombmaterial, a chemical-resistant film, a gas barrier film, acold-resistant film, an antibacterial sheet and film, a foamed sheet, arubber sheet, and the like may be used as other lamination units (B).Other lamination units (B) may be used singly or two or more of them maybe used in combination, if needed.

An example of a preferable embodiment of a preform composed of theaforementioned prepreg (A) and another lamination unit (B) include asandwich structure composed of a skin layer and a core layer.

Of such sandwich structures, a case that the skin layer has beenconstituted by the aforementioned prepreg (A) is preferred because amolded product to be obtained will exhibit isotropic properties and thefollowability to a complicated shape can be secured. In this case, fromthe viewpoint of further enhancing these effects, it is more preferableto use, as the core layer, a sheet-like base material, a porous basematerial, a honeycomb material, and a mat base material containingreinforcing fibers, which are lower in bulk density than the prepreg(A).

Of the sandwich structures, a case that the core layer is composed ofthe aforementioned prepreg (A) is preferable because the thickness of amolded product to be obtained can be rendered more uniform andimpartation of functions can be secured easily. In this case, from theviewpoint of increasing the rigidity effect, it is more preferable touse, as the core layer, a unidirectional base material containingcontinuous reinforcing fibers, a textile base material, and so on. Fromthe viewpoint of imparting functions to the surface of a molded product,it is more preferable to use a flame-retardant film, a decorative film,and so on.

Here, a molded product that is superior in mechanical properties and isin conformity with a complicated shape can be obtained also by a methodin which a preform to be obtained by laminating reinforcing fiber basematerials to be used for the prepreg of the present invention is set toa mold, and then RTM molding (resin transfer molding) is performed; anda method in which a preform to be obtained by laminating a reinforcingfiber base material to be used for the prepreg of the present inventionwith a unidirectional base material, a textile base material, or a matbase material is set to a mold, it is impregnated with a thermosettingresin, and RTM molding is performed. These can be expected to producethe same effect as that of the present invention.

Like the explanation of the handling performance of the prepregdescribed above, the preform of the present invention secures a stableworkability in a lamination step, and from the viewpoint of the handlingperformance of a preform in a molding step such as stable transfer to amold, it is preferable to inhibit thickness expansion. The hpn (mm) at(n×100)° C. preferably satisfies hp0≦hpn≦hp0×(2n+1) (hp0 (mm) representsthe thickness of the preform at 23° C., and n represents at least onenatural number selected from among 1, 2, 3 and 4), more preferablysatisfies hp0≦hpn≦hp0×2n, and particularly preferably satisfieshp0≦hpn≦hp0×(2n−1). The selection criterion of n to be used here is thesame as that of the prepreg described above, and a proper natural numbercan be selected depending upon the materials to be used.

Although the thickness hp0 (mm) of the preform of the present inventionis not particularly limited, from the viewpoint of handling performancein molding it is preferably from 0.8 to 100 mm, more preferably from 1.2to 10 mm, and particularly preferably from 1.5 to 5 mm. Although thereis no particular limitations with respect to the laminated number of theprepregs to be used for the preform of the present invention and thelaminated number of other lamination units, from the viewpoint of themanufacture efficiency and the economical efficiency in the laminationstep, the laminated number is preferably from 2 layers to 100 layers,more preferably from 4 layers to 50 layers, and particularly preferablyfrom 8 layers to 30 layers. If the laminated number is increased, thework load in the lamination step increases, but the degree of freedom indesign of the molded product of the present invention can be increasedif it is within a preferable range.

[Molded Product]

The molded product to be obtained by molding the prepreg or the preformof the present invention can be used for various parts or components,and it is preferable that the molded product be light in weight and alsobe superior in rigidity and strength in order to increase the range ofit applications. Moreover, it is preferable that the molded product besuperior also in the coefficient of linear expansion, which is an indexof dimensional stability.

As a specific index, it is preferable that the molded product have aspecific rigidity of from 1.5 to 5, which is a parameter indicating thedegree of lightness and is expressed by Ec^(1/3)×ρ⁻¹ where the flexuralmodulus and the specific gravity of the molded product are representedby Ec and ρ, respectively. Since steel and aluminum generally have aspecific gravity of 1.5 or less, the specific rigidity of the moldedproduct is preferably 1.5 or more in order to fall within a specificrigidity region that is better than that of those metal materials.Moreover, the specific rigidity is more preferably from 2.0 to 5, whichexceeds 2.0 over a general specific strength of magnesium, and even morepreferably is from 2.5 to 5. Furthermore, in order to make the design ofa molded product easier, the specific rigidity preferably has isotropy;as an index of the isotropy of the specific rigidity, the flexuralmodulus Ec satisfies EcMax≦EcMin×2 in a relationship between a maximumflexural modulus EcMax and a minimum flexural modulus EcMin each in thedirection of measurement. It is more preferable that EcMax≦EcMin×1.8,and even more preferable that EcMax≦EcMin×1.5.

As a specific index of the strength of a molded product, it ispreferable that σc/p be from 100 to 500 where the tensile strength andthe specific gravity of the molded product are represented by σc and ρ,respectively. The ratio is more preferably from 200 to 500 and morepreferably from 300 to 500. For the same reason as that described as tothe aforementioned specific rigidity, the aforementioned tensilestrength σc, as an index of the isotropy of the tensile strength,satisfies σcMax≦σcMin×2 in a relationship between a maximum tensilestrength σcMax and a minimum tensile strength σcMin each in thedirection of measurement. It is more preferable that σcMax≦σcMin×1.8,and even more preferable that σcMax≦σcMin×1.5.

As a concrete index regarding the coefficient of linear expansion, whichis a parameter that represents the dimensional stability of a moldedproduct, the coefficient of linear expansion Cc of the aforementionedmolded product is preferably from 1×10⁻⁶ to 20×10⁻⁵/K. It is morepreferably from 1×10⁻⁶ to 15×10⁻⁵/K, and even more preferably from1×10⁻⁶ to 10×10⁻⁵/K. For the same reason as that described as to theaforementioned specific rigidity, the aforementioned coefficient oflinear expansion, as an index of the isotropy of the coefficient oflinear expansion Cc, satisfies CcMax≦CcMin×2 in a relationship between amaximum coefficient of linear expansion CcMax and a minimum coefficientof linear expansion CcMin each in the direction of measurement. It ismore preferable that CcMax≦CcMin×1.8, and even more preferable thatCcMax≦CcMin×1.5.

In considering the wall thinness and the lightness, a molded product tobe obtained by molding the prepreg or preform of the present inventionpreferably has a maximum thickness of 2 mm or less. The maximumthickness is more preferably 1.5 mm or less, and even more preferably1.2 mm or less. The maximum thickness explained here means the largestthickness among the thicknesses of the respective flat portionsconstituting the molded product. The maximum thickness is determined bymeasuring the thickest part in a flat portion constituting the moldedproduct.

A molded product may vary in thickness because of the degree of freedomin shape design. As to the thickness variation, it is preferable thatthe thickness vary continuously. The “continuously” as referred toherein means that the thickness varies taperingly.

Moreover, the molded product preferably has an uneven shape in order toenhance the effect of increasing the rigidity by its shape or to imparta design effect caused by its shape. Specifically, it is preferable thatthe level difference between the standard surface of the molded productand the uneven surface forming the uneven shape be 3 mm or more. Thestandard surface refers to a flat portion which has the largest areaamong the flat portions forming the molded product. The uneven surfaceforming an uneven shape with the standard surface is a flat portion thatis substantially parallel to the standard surface and is formed to beseparated from the standard surface by one or more flat portions. Here,“to be substantially parallel” means that the degree of an angle formedby the standard surface with a target flat portion is 20° or less. Whenthe standard surface and the uneven surface are parallel to each other,the level difference between the standard surface and the uneven surfacecan be measured directly. However, when the standard surface and theuneven surface form together a certain angle, the largest differenceamong the level differences between the standard surface and respectivepoints P on the uneven surface is defined as the level differencebetween the standard surface and the uneven surface. The leveldifference between the standard surface and the uneven surface ispreferably 5 mm or more.

Considering various applications in addition to those described above,it is preferable to provide a complicated shape to a molded product. Forexample, when a box-like shape composed of many flat portions is formed,it is a shape in which flat portions have been joined by bent portions.The radius of curvature of the R portion at each of the bent portions,which is used for indicating the degree of bend, is preferably small.From the viewpoint of forming a more complicated shape, the radius ofcurvature of the R portion is preferably 5 mm or less.

From the viewpoint of forming a complicated shape in a molded product,it is preferable that the number of the bent portions be three or more.A bent shape of a simple molded product has one bent portion, and aC-shape and a simple S-shape each have two bent portions. Usually, mostof the complicatedly shaped molded products such as components have manybent portions. An index of a preferred number of bent portions is threeor more. A box-like molded product having a simple quadrangled shape haseight bent portions.

From the viewpoint of extending the application range of molded productsto various cases, housings, and components from the shape aspect, amolded product preferably has a vertex that is formed by three flatportions separated by bent portions. The vertex that is formed by threeflat portions separated by bent portions is a corner that is formed bythree flat portions.

Furthermore, from the viewpoint of increasing rigidity, the moldedproduct may be provided with a rib. Although the rib is not particularlyrestricted with respect to its shape, preferable examples of the ribinclude a linear rib, a T-shaped rib, and a cross-shaped rib. While theheight of the rib will be determined according to need, it is preferably10 mm or less from the viewpoint of the wall thinness of a moldedproduct. It is more preferably 5 mm or less.

From the viewpoint of securing lightness, the molded product may be ahollow body. In this case, a hollow molded product may be formed byjoining some molded products in conformity with the shape of the moldedproduct.

For the purpose of imparting further enhanced mechanical properties to amolded product, the molded product may be united with another moldedproduct. As such another molded product, a fiber-reinforced compositematerial comprising continuous reinforcing fibers and a resin preferablyhas been joined in order to enhance the mechanical properties. Forexample, it becomes possible to impart excellent mechanical propertiesor rigidity by joining a fiber-reinforced composite material resultingfrom hybridization of continuous reinforcing fibers with a thermosettingresin, such as epoxy resin, or a thermoplastic resin, such aspolypropylene and polyamide, to the surface of a molded product.

It is also permissible to unite molded products to be obtained bymolding the prepregs or preforms of the present invention. According toan intended purpose, an example is a product produced by uniting with ahigh strength while having increased the fiber mass content of anotherpiece.

From the viewpoint of extending the applications of molded products, itis preferable to join complicatedly-shaped molded products. Examples ofthe complicatedly-shaped molded product include complicatedly-shapedinjection molded products, such as edges, frames, bosses, ribs, hinges,and mounts. It is possible to extend applications in which superiormechanical properties of a molded product can be utilized.

The method for uniting is not particularly restricted, and examplesthereof include methods using an adhesive, heat welding, vibrationwelding, ultrasonic welding, and laser welding. In particular, heatwelding, vibration welding, ultrasonic welding, and laser welding arepreferred because of the ease of the process and the short moldingcycle.

Here, the type of the press molding can be selected depending upon themolded product to be obtained. Press molding is a method of obtaining amolded product by applying deformation, such as bend, shear andcompression, to the aforementioned laminated preform by using aprocessing machine, a tool, a jig for molding, or a subsidiary material,and examples of a molding form include deep drawing, flanging,coalgating, edge curling, and die punching. Among various press moldingmethods, an autoclave method, which is often used for manufacturingmolded components for huge air planes and the like, and a mold pressingmethod, which has relatively simple and easy steps are preferably usedas the method of press molding. From the viewpoint of the facility, theamount of energy to be used in a molding step, the simplification of thejig for molding, the subsidiary materials to be used, the degree offreedom in molding pressure and in molding temperature, the use of moldpressing method in which molding is conducted by using a metal mold ismore preferred.

As a mold pressing method can be adopted a hot pressing method thatcomprises placing in advance the aforementioned prepreg or preform in amold, performing pressurization and heating together with mold clamping,and cooling the prepreg or preform by cooling the mold while continuingthe mold clamping, thereby obtaining a molded product, or when the resinof a prepreg or preform is a thermoplastic resin, stamping molding,which is a method that comprises heating in advance the prepreg orpreform to a temperature that is equal to or higher than the meltingtemperature of the thermoplastic resin by a heating device, such as afar-infrared heater, a hot plate, a high-temperature oven and dielectricheating, placing it on a mold member that is to be a lower surface ofthe mold while keeping the thermoplastic resin molten and softened, thenclosing the mold to perform mold clamping, and then pressurizing andcooling. The press molding method, which is not particularly restricted,is preferably stamping molding from the viewpoint of accelerating themolding cycle to increase the manufacture efficiency.

Moreover, in order to bring a prepreg or a preform into a shapeablestate, the resin is preferably a thermoplastic resin. The preheatingtemperature is preferably adjusted to equal to or higher than themelting point or softening point of the thermoplastic resin.

In conveying the preheated prepreg or preform to a mold to be used forpress molding, it is preferable to convey it quickly in order to performpress molding while keeping the preheated state sufficiently.Specifically, the time to be taken for preheating a prepreg or apreform, then conveying it to a mold, and starting pressurization bypress molding is preferably within 1 minute, more preferably within 30seconds, and even more preferably within 15 seconds.

The pressurization in a press mold is not particularly restricted, butfrom the viewpoint of shaping a prepreg or a preform well, thepressurizing force is preferably 0.1 MPa or more. It is more preferably1 MPa or more, and even more preferably 10 MPa or more. Although theupper limit of the pressurizing force is not particularly limited, 100MPa or less is a preferable range from the viewpoint of inhibiting thebreakage of reinforcing fibers during molding.

There are no particular limitations as to the cooling in a press mold,but when a thermoplastic resin is used as the resin constituting aprepreg or a preform, it is preferable to adjust the surface temperatureof the mold to equal to or lower than the melting point or softeningpoint of the thermoplastic resin from the viewpoint of cooling thepreheated preform sufficiently. Moreover, from the viewpoint ofadvancing the release from the mold and shortening the molding cycle, itis preferable to adjust the mold temperature to be lower than themelting point or softening point of the thermoplastic resin by 30° C. ormore, more preferably by 50° C. or more.

Next, a step of placing the prepreg or preform of the present inventionin a mold and press molding it is described. For the prepreg or preformof the present invention, it is preferable to place it in the mold whileadjusting the charge ratio expressed by the following formula to higherthan 100%.

Charge ratio (%)=100×(area of prepreg or preform)/(total area of moldcavity).

By placing, in the mold, a prepreg or preform having a charge ratio thatis higher than 100%, in other words, a prepreg or preform that is largerthan a size to cover the whole area of the mold cavity, it becomespossible to do molding while keeping fiber orientation without causingexcessive flow of the prepreg or preform during molding. Therefore, itis possible to obtain a molded product that makes the most of the fiberorientation of a prepreg or preform while inhibiting, as much aspossible, disturbance of fiber orientation during molding or generationof anisotropy in fiber orientation caused by the flow occurring duringmolding. The charge ratio is adjusted preferably to 105% or more andmore preferably to 110% or more. The upper limit of the charge ratio,which is not particularly limited, is preferably up to 150% from theviewpoint of using materials effectively and avoiding waste.

Next, the mold to be used for molding is explained. Molds are classifiedroughly into two categories; one is a closed mold, which is to be usedfor casting, injection molding, etc., and another is an open mold, whichis to be used for press molding, forging, etc. The closed mold is a moldthat performs molding mainly by pouring a material to the insidethereof, whereas the open mold is a mold that performs molding mainly bydeforming a material without pouring it. The use of an open mold ispreferred in order to obtain a molded product with which the fiberorientation of a prepreg or preform is harnessed while inhibiting thefiber orientation of the prepreg or preform as much as possible fromfalling into disorder during molding or inhibiting the anisotropy in thefiber orientation as much as possible from being caused by the flow thatoccurs during the molding without causing excessive flow in a basematerial during the molding. Moreover, the open mold is preferred alsofrom the viewpoint of removing the gas decomposed or the air entrainedduring the molding to the outside of the mold.

Furthermore, preferred is a mold that has at least one selected fromamong a stamping-out mechanism, a punching mechanism, and a tappingmechanism. The molded product produced by press molding may have beenpress formed with a charge percentage of a prepreg or preform of greaterthan 100% relative to the total cavity area of the mold or may have botha portion that is necessary as a molded product and an unnecessaryportion (edge portion). Therefore, a step of removing the edge portionmay become necessary in order to finish the shape of a molded productafter molding. A molded product is expected to be processed, dependingupon the purpose of the usage thereof, into a molded product having avent hole or an exhaust hole for generated gas or heat exchange, a gripportion of a molded product, a screwhole for processing or a hole forbolt connection, a hole aiming at imparting design, or a hole portion tobe used for punch patterns. It is preferable to have at least oneselected from among the aforementioned three mechanisms because if so, astep of removing an edge portion after press molding or a step offorming a necessary hole portion can be performed simultaneously withpress molding, so that simplification of a process can be achieved.

Examples of the applications of molded products to be produced by usingthe prepreg or preform of the present invention include electricinstrument components, electronic instrument components, components forcivil engineering, components for building materials, structuralcomponents for cars, structural components for motorcycles, componentsfor cars, components for motorcycles, and components for airplanes. Fromthe viewpoint of mechanical properties, the molded products are suitablyused for housings of electric or electronic instruments, panels forcivil engineering or building materials, structural components of cars,and components of airplanes. Particularly from the viewpoint of physicalcharacteristics and isotropy, the molded products are suitably used forstructural units for cars and motorcycles.

EXAMPLES

The present invention will be described below in more detail withreference to Examples.

[Evaluation (1) of Prepreg, Preform, and Molded Product]

(1) Evaluation of the Length of Reinforcing Fibers Contained in Prepreg

A prepreg was heated at 500° C. in the air for one hour, thereby burningoff a resin component. Four hundred remaining reinforcing fibers wereselected at random, the length thereof was measured down to 1 μm, andthen the fiber lengths and the proportions thereof were measured.Moreover, the reinforcing fiber length distribution was evaluated bycounting the frequency of reinforcing fibers at 0.25 mm intervals, suchas shorter than 0.25 mm, 0.25 mm or longer and shorter than 0.5 mm, and0.5 mm or longer and shorter than 0.75 mm.

(2) Measurement of the Two-Dimensional Orientation Angle of ReinforcingFibers in Prepreg

As depicted in FIG. 2, a prepreg was sandwiched between two sheets ofstainless steel mesh (plain woven shape with 50 meshes per 2.5 cm) andthey were fixed with adjustment of a screw so that the prepreg might notmove. This was heated at 500° C. in the air for one hour, therebyburning off a resin component. Then, the stainless steel mesh sheetswere removed and the resulting reinforcing fiber base material wasobserved with a microscope. One reinforcing filament (a) was selected atrandom, and the two-dimensional orientation angle formed by thereinforcing filament and another one intersecting therewith was measuredby image observation. Of two angles formed by the two intersectingreinforcing filaments, an angle of 0° or more and 90° or less (i.e., anacute angle) was adopted as the orientation angle. The number ofmeasurement of the two-dimensional orientation angle for one reinforcingfilament (a) selected was n=20. The same measurement was conducted byselecting five reinforcing filaments in total and the average of themeasurements was defined as the two-dimensional orientation angle.

(3) Amount of Air of Reinforcing Fiber Base Material (Frazier Method)

Using a reinforcing fiber base material obtained in the same manner asthat in the burning off of (2) described above, the amount of airmeasured by the Frazier type method based on ASTM D737 (2008 edition)was measured.

(4) Fiber Mass Content Wf (%) of Reinforcing Fibers in Prepreg

After the mass W1 of a prepreg was measured, the prepreg was heated at500° C. in the air for one hour, so that resin components were burnedoff. The mass W2 of the remaining reinforcing fibers was measured, andcalculation was conducted by the following formula:

Wf(%)=100×W2/W1.

(5) Thickness hn of Prepreg, and Thickness hpn of Preform (hn, hpn (n=0,1, 2, 3, 4))

A prepreg or a preform was left at rest in the air for 10 minutes at atemperature at which measurement would be conducted, and then it wascooled to room temperature. In the prepreg or the preform, two point Xand Y were determined so that the straight distance XY would become thelongest, the thickness was measured at each of the dividing points whichdivided the straight line XY into ten equal segments except both ends X,Y. The average thereof was defined as the thickness hn or hpn of theprepreg or the preform.

(6) Bulk Density of Prepreg

A square prepreg of 100 mm on each side was cut out and its mass W wasmeasured. Then, a bulk density was calculated from the followingformula:

Bulk density of prepreg=W/(10×10×h0) where h0 is the thickness of theprepreg.

(7) Resin Impregnation Ratio % of Prepreg

A resin impregnation ratio of a prepreg was measured by observing asection in the thickness direction of the prepreg as follows. Theprepreg was wrapped with an epoxy resin, and then a surface which was asectional end of the prepreg was polished. An area defined by (thethickness of the prepreg)×a width of 500 μm of the polished surface wasphotographed at a magnification of 400 by the use of a super-deep color3D profile measurement microscope VK-9500 (controller)/VK-9510(measuring part) (manufactured by KEYENCE Corporation). In an observedimage, the area of sites where the resin had penetrated and the area ofsites where the resin had not penetrated were determined, and then aresin impregnation ratio was calculated by using the following formula:

Resin impregnation ratio (%)=100×(the total area of sites where theresin has penetrated)/(the cross sectional area of the observed site ofthe prepreg exclusive of reinforcing fiber portions)=100×(the area ofsites where the resin has penetrated)/((the area of (the thickness ofthe prepreg)×(a width of 500 μm)−the area of reinforcing fiberportions).

(8) Tensile Strength σ of Prepreg

Specimens were cut from a prepreg, and the tensile characteristicthereof was measured in accordance with the ISO 527-3 method (1995).Regarding the specimens, specimens which had been cut in fourdirections, i.e., 0°, which was an arbitrary direction, +45°, −45°, and90° directions, were prepared, and an average value of all measurements(n=20) obtained at the number of measurements n=5 for each of thedirections was defined as a tensile strength σ. As a measuringinstrument was used “Instron (registered trademark)” 5565 type universaltesting instrument (manufactured by Instron Japan Company, Ltd.).

(9) Tensile Strength σMax, σMin

Among the 20 measurements of tensile strength σ measured in the above(8), the maximum value and the minimum value were expressed by σMax andσMin, respectively.

(10) Specific Strength of Molded Product

A specimen was cut from of a molded product and the specific gravity ρof the molded product was measured on the basis of ISO 1183 (1987).Subsequently, specimens were cut from the molded product and the tensilestrength thereof was measured in accordance with the ISO 527-3 method(1995). Regarding the specimen, specimens were prepared which had beencut in four directions, i.e., 0°, +45°, −45°, and 90° directions, wherean arbitrary direction was determined as 0°. Then, an average value ofall measurements (n=20) obtained at the number of measurements n=5 foreach of the directions was defined as a tensile strength σc. As ameasuring instrument was used “Instron (registered trademark)” 5565 typeuniversal testing instrument (manufactured by Instron Japan Company,Ltd.). On the basis of the result obtained, the specific strength of themolded product was calculated by the following formula.

Specific strength of molded product=σc/ρ.

(11) σcMax and σcMin of the Tensile Strength of Molded Product

Among 20 tensile strengths ac measured in (10) described above, themaximum value was expressed by σcMax and the minimum value was expressedby σcMin.

(12) Specific Rigidity of Molded Product

Specimens were cut from a prepreg, and then the flexural moduli thereofwere measured in accordance with the ISO 178 method (1993). Regardingthe specimen, specimens were prepared which had been cut in fourdirections, i.e., 0°, +45°, −45°, and 90° directions, where an arbitrarydirection was determined as 0°. Then, an average value of allmeasurements (n=20) obtained at the number of measurements n=5 for eachof the directions was defined as a flexural modulus Ec. As a measuringinstrument was used “Instron (registered trademark)” 5565 type universaltesting instrument (manufactured by Instron Japan Company, Ltd.). On thebasis of the result obtained, the specific rigidity of the moldedproduct was calculated by the following formula.

Specific rigidity of molded product=Ec^(1/3)/ρ

ρ: Specific gravity of molded product.

(13) EcMax and Ecmin of the Flexural Modulus of Molded Product

Among 20 flexural moduli measured in (12) described above, the maximumvalue was expressed by EcMax and the minimum value was expressed byEcMin.

(14) Interlaminar Shear Strength of Laminated Perform

Specimens were cut from a laminated preform, so that specimens of 6.4 mmin width and 14 mm in length were produced in accordance with ASTMD2344, and then a three-point test was performed at n=10 to measureinterlaminar shear strength. The average of n=10 was adopted as aresult.

(15) Coefficient of Linear Expansion of Molded Product

Specimens were cut from of a molded product and the coefficient oflinear expansion thereof was measured on the basis of ISO 11359-2.Regarding the specimens, specimens which had been cut in fourdirections, i.e., 0°, which was an arbitrary direction, +45°, −45°, and90° directions, were prepared, and an average value obtained at thenumber of measurements n=5 for each of the directions was defined as acoefficient of linear expansion Cc.

(16) CcMax and CcMin of the Coefficient of Linear Expansion of MoldedProduct

Among the coefficients of linear expansion measured in all fourdirections of 0°, +45°, −45°, and 90° in the molded product to measure,the maximum value is expressed by CcMax and the minimum value isexpressed by CcMin.

(17) Judgment of the Specific Strength of Molded Product

Judgment was done according to the following criteria on the basis ofthe coefficient of linear expansion of a molded product.

A: The specific strength was 300 MPa or more.

B: The specific strength was 200 MPa or more and less than 300 MPa.

C: The specific strength was 150 MPa or more and less than 200

MPa.

D: The specific strength was less than 150 MPa.

(18) Judgment of the Specific Rigidity of Molded Product

Judgment was done according to the following criteria on the basis ofthe specific rigidity of a molded product.

AAA: The specific rigidity was 3.00 or more.

AA: The specific rigidity was 2.50 or more and less than 3.00.

A: The specific rigidity was 2.20 or more and less than 2.50.

B: The specific rigidity was 2.00 or more and less than 2.20.

A: The specific rigidity was 1.50 or more and less than 2.00.

D: The specific rigidity was less than 1.50.

(19) Judgment of the Coefficient of Linear Expansion of Molded Product

Judgment was done according to the following criteria on the basis of acoefficient of linear expansion of a molded product.

A: The coefficient of linear expansion was 7×10⁻⁶/K or less.

B: The coefficient of linear expansion was more than 7×10⁻⁶/K and10×10⁻⁶/K or less.

C: The coefficient of linear expansion was more than 10×10⁻⁶/K and20×10⁻⁶/K or less.

D: The coefficient of linear expansion was more than 20×10⁻⁶/K.

(20) Judgment of the Isotropy of Molded Product

Judgment was done according to the following criteria on the basis ofthe in-plane variation of the respective properties, i.e., tensilestrength, flexural modulus, and coefficient of linear expansion of amolded product.

AA: The maximum was not smaller than 1.0 time and not larger than 1.1times the minimum.

A: The maximum was larger than 1.1 times and not larger than 1.3 timesthe minimum.

B: The maximum was larger than 1.3 times and not larger than 2 times theminimum.

D: The maximum was larger than 2 times the minimum.

(Material 1) Carbon Fiber 1

A copolymer containing polyacrylonitrile as a main component wassubjected to spinning, a baking treatment, and a surface oxidationtreatment, yielding continuous carbon fibers having a total number offilaments of 12,000. The properties of this continuous carbon fiber wereas follows.

-   -   Filament diameter: 7    -   Mass per unit length: 1.6 g/m    -   Specific gravity: 1.8    -   Tensile strength: 4600 MPa    -   Tensile modulus: 220 GPa.

(Material 2) Carbon Fiber 2

A copolymer containing polyacrylonitrile as a main component wassubjected to spinning, a baking treatment, and a surface oxidationtreatment, yielding continuous carbon fibers having a total number offilaments of 12,000. The properties of this continuous carbon fiber wereas follows.

-   -   Filament diameter: 7 μm    -   Mass per unit length: 1.6 g/m    -   Specific gravity: 1.8    -   Tensile strength: 4100 MPa    -   Tensile modulus: 420 GPa.

(Material 3) Carbon Fiber 3

TORAYCA T700S-12-50C, produced by Toray Industries, Inc.

(Material 4) Glass Fiber

Commercial name PF-E001, produced by Nitto Boseki Co., Ltd.

(Material 5) Glass Fiber-Reinforced Thermoplastic Resin (GMT)

UNISHEET P4038-BK31 produced by Quadrant. The thickness was 3.8 mm.

(Material 6) PP Resin Sheet

A resin sheet having a thickness of 1 mm was produced which was composedof 50% by mass of an unmodified polypropylene resin (“Prime Polypro”J105G, produced by Prime Polymer Co., Ltd.) and 50% by mass of anacid-modified polypropylene resin (“ADMER” QB510, produced by MitsuiChemicals, Inc.).

(Material 7) Foamed PP Resin Sheet

Commercial name: EFCELL (two-time expansion, 1 mm in thickness),produced by Furukawa Electric Co., Ltd.

(Material 8) Transparent Nylon Resin Film

A transparent nylon resin film (transparent Ny, 50 μm in thickness) madeof Crystamid MS1100, produced by Tokyo Zairyo Co., Ltd., was produced.

(Material 9) Nylon Resin Flame-Retardant Film

A Nylon 6 resin flame-retardant film (flame-retardant Ny, 50 μm inthickness) was obtained by mixing 10 parts by mass of Novaled 120(average particle diameter: 25 μm, phosphorus content: 85%) produced byRinkagaku Kogyo Co., Ltd., to 100 parts by mass of CM1007 (Nylon 6resin) produced by Toray Industries, Inc., followed by kneading. Theflame retardancy of this film was UL94 and VTM-0.

(Material 10) Continuous Carbon Fiber Prepreg

TORAYCA PREPREG P3052S-12 produced by Toray Industries, Inc.

(Material 11) Carbon Fiber Sheet Molding Compound (SMC)

Material 3, that is, TORAYCA T700S-12K-50C was cut into a length of 25mm, and the cut carbon fiber bundle was spread so that the carbon fiberbundle might distribute in random directions. Thus, acarbon-fiber-bundle-randomly-oriented base material was produced. Then,a carbon fiber sheet molding compound base material (SMC) was producedby impregnating 60 parts by mass of thecarbon-fiber-bundle-randomly-oriented base material with 40 parts bymass of the following vinyl ester resin for carbon fiber sheet moldingcompounds. The thickness was 2 mm.

-   -   Vinyl ester resin: a product containing Ripoxy H600 that was        produced by Showa Highpolymer Co., Ltd., as a matrix resin and        that was obtained by mixing, to 100 parts by mass of the        vinylester resin, 1.0 part by mass of an organic peroxide curing        agent (PERBUTYL Z produced by by Nippon Oil & Fats Co., Ltd.),        0.6 parts by mass of a polymerization inhibitor (TBH produced by        Seiko Chemical Co., Ltd.), 13.0 parts by mass of a thickener        (I-143L, produced by The Dow Chemical Co., Ltd.), and 5.0 parts        by mass of an internal release agent (ZNS-P produced by ADEKA        FINE).

(Material 12) Carbon Fiber Prepreg with Cut

A cut-in carbon fiber prepreg having regular cuts provided at equalintervals was obtained by successively forming cuts illustrated in FIG.7 into a TORAYCA PREPREG P3052S-17 produced by Toray Industries, Inc.,by the use of an automatic cutting machine. The cutting direction is adirection 13 perpendicular to fibers, the length 17 of each cut is 5.1mm, and the interval 18 (fiber length) is 30 mm. 19, over which cuts ofadjacent lines overlap with each other, is 0.1 mm.

(Material 13) Epoxy Resin 1

A blend of 40 parts by mass of EPOTOHTO YD128 (produced by Tohto KaseiCo., Ltd.), 20 parts by mass of EPOTOHTO YD128G (produced by Tohto KaseiCo., Ltd.), 20 parts by mass of EPICOAT 1001 (produced by Japan EpoxyResins Co., Ltd.), and 20 parts by mass of EPICOAT 1009 (produced byJapan Epoxy Resins Co., Ltd.) as epoxy resins, 4 parts by mass of DICY7(dicyandiamide, produced by Japan Epoxy Resins Co., Ltd.) and 3 parts bymass of DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethylurea, produced byHodogaya Chemical Co., Ltd.) as curing agents, and 5 parts by mass ofVINYLEC K (polyvinyl formal, produced by Chisso Corp.) as an additive.The glass transition temperature of an uncured resin is 3° C. Theviscosity at 60° C. is 200 Pa·s.

(Material 14) Epoxy Resin 2

A blend of 70 parts by mass of EPOTOHTO YD128 (produced by Tohto KaseiCo., Ltd.), 30 parts by mass of EPICOAT 1009 (produced by Japan EpoxyResins Co., Ltd.) as epoxy resins, 4 parts by mass of DICY7(dicyandiamide, produced by Japan Epoxy Resins Co., Ltd.) and 3 parts bymass of DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethylurea, produced byHodogaya Chemical Co., Ltd.) as curing agents, and 5 parts by mass ofVINYLEC K (polyvinyl formal, produced by Chisso Corp.) as an additive.The viscosity when the glass transition temperature of an uncured resinis 60° C. is 600 Pa·s.

(Material 15) Chopped Fiber of Nylon 6 Resin

A Nylon 6 resin fiber (filament fineness: 3 dtex) obtained by spinningCM1007 (Nylon 6 resin) produced by Toray Industries, Inc., was cut into5.0 mm with a cartridge cutter, so that a Nylon 6 resin chopped fiberwas obtained.

Example 1

The carbon fiber 1 obtained in Material 1 was cut into 6 mm with acartridge cutter, so that chopped carbon fiber was obtained. Adispersion liquid with a concentration of 0.1% by mass composed of waterand a surfactant (polyoxyethylene lauryl ether (commercial name),produced by Nacalai Tesque, Inc.) was prepared. A carbon fiber basematerial was produced using the apparatus for manufacturing areinforcing fiber base material (papermaking base material) of FIG. 3and using this dispersion liquid and the aforementioned chopped carbonfiber. The manufacture apparatus is composed of a dispersion vessel 21,a papermaking vessel 22, and a conveyor 32. The dispersion vessel 21 isa container in a cylindrical form of 1000 mm in diameter and has astraight transport portion (the inclination angle is 30°) with anopening cock at a lower portion of the container. The transport portionconnects the dispersion vessel and the papermaking vessel. A stirrer ismounted to the upper opening of the dispersion vessel, and choppedcarbon fibers and a dispersion liquid (dispersion medium) can be chargedthrough the opening. The papermaking vessel has, at its bottom, a meshconveyor with a papermaking surface having a width of 500 mm. Theconveyor 32 is disposed following a mesh conveyor 31 and conveys acarbon fiber base material 30. Papermaking was performed while adjustingthe carbon fiber concentration in the dispersion liquid to be 0.05% bymass. The carbon fiber base material prepared by papermaking was driedin a drying oven of 200° C. for 30 minutes. The resulting carbon fiberbase material had a width of 500 mm, a length of 500 mm, and a basisweight of 50 g/m². The properties of the reinforcing fiber base materialare shown in Table 1.

One sheet of the above-mentioned carbon fiber base material waslaminated with two films of CM1007 (Nylon 6 resin) of the same thicknessso that it might become film/carbon fiber base material/film. A pressureof 5 MPa was added to the resulting laminated article at a temperatureof 250° C. for two minutes to prepare a prepreg (1) of 500 mm in widthand 500 mm in length in which the Nylon 6 resin had been penetrated intothe carbon fiber base material were produced. The properties of theprepreg are shown in Table 2.

A preform (A) in which eight prepregs (1) had been laminated wasprepared and then preheated at 280° C. under a nitrogen atmosphere in afar-infrared heating oven. The preform (A) was placed in a stamping moldwhose cavity surface temperature was 120° C. and which had an L-shapedbox-like cavity of the B5 size illustrated in FIG. 4 having a thicknessof 1.1 mm (the charge ratio was 110%). Then, the mold was closed, and apressure was added at a molding pressure of 30 MPa and held for twominutes. Then, the mold member was opened and ejection was performed, sothat an L-shaped box-like molded product was obtained. The preform (A)was shaped well inconformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 3 and Table 10.

Example 2

A prepreg (2) was produced in the same manner as in Example 1 exceptthat the Nylon 6 resin with which the carbon fiber base material was tobe impregnated was adjusted so that the fiber mass content might become52%. The properties of the prepreg are shown in Table 2. An L-shapedbox-like molded product was produced in the same manner as in Example 1except for manufacturing a preform in which seventeen prepregs (2) hadbeen laminated. The preform was shaped well in conformity with the shapeof the mold and a molded product that was high in shape quality wasobtained. The properties of the molded product are shown in Table 3.

Example 3

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the basis weight of the carbon fiber basematerial to 70 g/m² by adjusting the flow rate of the dispersion liquidand the speed of the mesh conveyer during papermaking. The properties ofthe reinforcing fiber base material are shown in Table 1. The Nylon 6resin film with which this carbon fiber base material was to beimpregnated was adjusted so that the fiber mass content might become 65%and a pressure of 5 MPa was applied at a temperature of 270° C. forthree minutes, so that a prepreg (3) in which the carbon fiber basematerial had been impregnated with the Nylon 6 resin was produced. Sincethe fiber mass content was high, the impregnation with the resin becamea little difficult. The properties of the prepreg are shown in Table 2.An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which seventeenprepregs (3) had been laminated. The preform was shaped well inconformity with the shape of the mold and a molded product that was highin shape quality was obtained. The properties of the molded product areshown in Table 3.

Example 4

A prepreg (4) was produced in the same manner as in Example 1 exceptthat the Nylon 6 resin film with which the carbon fiber base materialwas to be impregnated was adjusted so that the fiber mass content mightbecome 15%. The properties of the prepreg are shown in Table 2. AnL-shaped box-like molded product was produced in the same manner as inExample 1 except for manufacturing a preform in which four prepregs (4)had been laminated. The preform was shaped well in conformity with theshape of the mold and a molded product that was high in shape qualitywas obtained. The properties of the molded product are shown in Table 3.

Example 5

A prepreg (5) was produced in the same manner as in Example 1 exceptthat the Nylon 6 resin film with which the carbon fiber base materialwas to be impregnated was adjusted so that the fiber mass content mightbecome 8%. The properties of the prepreg are shown in Table 2. AnL-shaped box-like molded product was produced in the same manner as inExample 1 except for manufacturing a preform in which two prepregs (5)had been laminated. The preform was shaped well in conformity with theshape of the mold and a molded product that was high in shape qualitywas obtained. The properties of the molded product are shown in Table 3.

Example 6

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the speed of the mesh conveyer at thetime of papermaking to four times the flow rate of the dispersionliquid. The properties of the reinforcing fiber base material are shownin Table 1. Using the resulting carbon fiber base material, a prepreg(6) which the Nylon 6 resin had penetrated was produced in the samemanner as in Example 1. The properties of the prepreg are shown in Table2. An L-shaped box-liked molded product was produced in the same manneras in Example 1 except for using the prepreg (6). The preform was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The properties of the moldedproduct are shown in Table 3.

Example 7

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the basis weight of the carbon fiber basematerial to 20 g/m² by adjusting the flow rate of the dispersion liquidand the speed of the mesh conveyer during papermaking. The properties ofthe reinforcing fiber base material are shown in Table 1. The Nylon 6resin film with which this carbon fiber base material was to beimpregnated was adjusted so that the fiber mass content might become 20%and a pressure of 5 MPa was applied at a temperature of 250° C. for twominutes, so that a prepreg (7) in which the carbon fiber base materialhad been impregnated with the Nylon 6 resin was produced. The propertiesof the prepreg are shown in Table 2. An L-shaped box-like molded productwas produced in the same manner as in Example 1 except for manufacturinga preform in which eight prepregs (7) had been laminated and using astamping mold that had a cavity with a thickness of 0.4 mm in the sameshape as that illustrated in FIG. 4 (L-shaped box-like form of the B5size). The preform was shaped well in conformity with the shape of themold and a molded product that was high in shape quality was obtained.The properties of the molded product are shown in Table 3.

Example 8

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the basis weight of the carbon fiber basematerial to 10 g/m² by adjusting the flow rate of the dispersion liquidand the speed of the mesh conveyer during papermaking. The properties ofthe reinforcing fiber base material are shown in Table 4. The Nylon 6resin film with which this carbon fiber base material was to beimpregnated was adjusted so that the fiber mass content might become 20%and a pressure of 5 MPa was applied at a temperature of 250° C. for twominutes, so that a prepreg (8) in which the carbon fiber base materialhad been impregnated with the Nylon 6 resin was produced. The propertiesof the prepreg are shown in Table 5. An L-shaped box-like molded productwas produced in the same manner as in Example 7 except for manufacturinga preform in which sixteen prepregs (8) had been laminated. Since theprepregs (8) were very thin, the number of the laminated prepregs waslarge and therefore much time was taken for lamination, but the preformwas shaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 6.

Example 9

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the basis weight of the carbon fiber basematerial to 200 g/m² by adjusting the flow rate of the dispersion liquidand the speed of the mesh conveyer during papermaking. The properties ofthe reinforcing fiber base material are shown in Table 4. The Nylon 6resin film with which this carbon fiber base material was to beimpregnated was adjusted so that the fiber mass content might become 20%and a pressure of 5 MPa was applied at a temperature of 250° C. for twominutes, so that a prepreg (9) in which the carbon fiber base materialhad been impregnated with the Nylon 6 resin was produced. The propertiesof the prepreg are shown in Table 5. An L-shaped box-like molded productwas produced in the same manner as in Example 1 except for manufacturinga preform in which two prepregs (9) had been laminated. The preform wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 6.

Example 10

A carbon fiber base material was produced in the same manner as inExample 1 except for using, in papermaking, chopped carbon fiberscomposed of a mixture of chopped carbon fibers having a length of 6 mmand chopped carbon fibers having a length of 3 mm in a mass ratio of1:1. The properties of the reinforcing fiber base material are shown inTable 4. Using the resulting carbon fiber base material, a prepreg (10)which the Nylon 6 resin had penetrated was produced in the same manneras in Example 1. The properties of the prepreg are shown in Table 5.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using the prepreg (10). The preform was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The properties of the moldedproduct are shown in Table 6.

Example 11

A carbon fiber base material was produced in the same manner as inExample 1 except for using, in papermaking, chopped carbon fiberscomposed of a mixture of chopped carbon fibers 2 having a length of 6 mmand chopped carbon fibers 1 having a length of 3 mm in amass ratio of3:1. The properties of the reinforcing fiber base material are shown inTable 4. Using the resulting carbon fiber base material, a prepreg (11)which the Nylon 6 resin had penetrated was produced in the same manneras in Example 1. The properties of the prepreg are shown in Table 5.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using the prepreg (11). The preform was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The properties of the moldedproduct are shown in Table 6.

Example 12

A prepreg (12) was produced in the same manner as in Example 1 exceptthat the pressure and the time were adjusted when the carbon fiber basematerial was impregnated with the Nylon 6 resin film so that the resinimpregnation ratio might become 20%. The properties of the prepreg areshown in Table 5. An L-shaped box-liked molded product was produced inthe same manner as in Example 1 except for using the prepreg (12),adjusting the cavity surface temperature of the mold to 270° C., addinga molding pressure of 35 MPa and holding it 10 minutes. Although it wasnecessary to increase the molding temperature, the molding pressure andthe molding time because the resin impregnation ratio of the preform waslow, the molded product was shaped well in conformity with the shape ofthe mold and a molded product that was high in shape quality wasobtained. The properties of the molded product are shown in Table 6.

Example 13

The carbon fiber base material of Example 1 and two films of the samethickness made of A900 (PPS resin) produced by Toray Industries, Inc.,as films were used and laminated so as to form film/carbon fiber basematerial/film, and a pressure of 5 MPa was applied for 2 minutes at atemperature of 300° C. Thus, a prepreg (13) composed of the carbon fiberbase material impregnated with the PPS resin was prepared. Theproperties of the prepreg are shown in Table 5.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using the prepreg (13), and adjusting the cavitysurface temperature of the mold to 300° C. The molded product was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The properties of the moldedproduct are shown in Table 6.

Example 14

The carbon fiber base material of Example 1 and two films of the samethickness prepared from a resin prepared by kneading 50% by mass of anunmodified polypropylene resin (“Prime Polypro” J105G, produced by PrimePolymer Co., Ltd.) and 50% by mass of an acid-modified polypropyleneresin (“ADMER” QB510, produced by Mitsui Chemicals, Inc.) as films wereused and laminated so as to form film/carbon fiber base material/film,and a pressure of 5 MPa was applied for 2 minutes at a temperature of230° C. Thus, a prepreg (14) composed of the carbon fiber base materialimpregnated with a PP resin was prepared. The properties of the prepregare shown in Table 5.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using the prepreg (14), and adjusting the cavitysurface temperature of the mold to 230° C. The molded product was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The properties of the moldedproduct are shown in Table 6.

Referential Example 1

The carbon fiber base material of Example 1 and two films of the samethickness made of the epoxy resin of Material 13 as films were used andlaminated so as to form film/carbon fiber base material/film, and apressure of 5 MPa was applied for 2 minutes at a temperature of 60° C.Thus, a prepreg (15) composed of the carbon fiber base materialimpregnated with the epoxy resin 1 was prepared. As compared with caseswhere thermoplastic resins are used, the tensile strength of the prepregwas low, and therefore it became difficult to handle the prepreg in alamination step. The properties of the prepreg are shown in Table 8.

An L-shaped box-like molded product was produced by using the prepreg(15), molding it while adjusting the cavity surface temperature of themold to 150° C., the molding pressure to 10 MPa and the molding time to30 minutes, and then performing release from the mold. The moldedproduct was shaped well in conformity with the shape of the mold and amolded product that was high in shape quality was obtained. Theproperties of the molded product are shown in Table 9.

Referential Example 2

The carbon fiber base material of Example 1 and two films of the samethickness made of the epoxy resin of Material 14 as films were used andlaminated so as to form film/carbon fiber base material/film, and apressure of 5 MPa was applied for 2 minutes at a temperature of 60° C.Thus, a prepreg (16) composed of the carbon fiber base materialimpregnated with the epoxy resin 1 was prepared. As compared with caseswhere thermoplastic resins are used, the tensile strength of the prepregwas low, and therefore it became difficult to handle the prepreg in alamination step. The properties of the prepreg are shown in Table 8.

An L-shaped box-liked molded product was produced in the same manner asin Example 14 except for using the prepreg (16). The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 9.

Example 15

There was prepared a film using a Nylon 6 obtained by mixing 10 parts bymass of Novaled 120 (average particle diameter: 25 μm, phosphoruscontent: 85%) produced by Rinkagaku Kogyo Co., Ltd., to 100 parts bymass of CM1007 (Nylon 6 resin) produced by Toray Industries, Inc.,followed by kneading. A prepreg (17) was produced in the same manner asin Example 1 except for using the carbon fiber base material of Example1 and the two films of the same thickness and laminating them so as toform film/carbon fiber base material/film. The properties of the prepregare shown in Table 8.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using the prepreg (17). The preform was shapedwell in conformity with the shape of the mold and a molded product thatwas high in shape quality was obtained. The molded product was one towhich flame retardancy had been imparted by the incorporation of redphosphorus. The flame retardancy was UL94V-0. The properties of themolded product are shown in Table 9.

Example 16

A prepreg (18) was produced in the same manner as in Example 1 exceptfor adjusting the size of the prepreg to 1000 mm×500 mm. The propertiesof the prepreg are shown in Table 8.

A molded product in the form of a bonnet of an automobile was producedin the same manner as in Example 1, except for preparing a preform inwhich 24 prepregs (18) had been laminated and using a mold forautomobile bonnet molded product as shown in FIG. 8. The preform, whichwas large in size, could be handled in lamination, transportation, andso on, and it was shaped well in conformity with the shape of the moldand a molded product that was high in shape quality was obtained. Theproperties of the molded product are shown in Table 9.

Example 17

A glass fiber base material was obtained in the same manner as inExample 1, except for using chopped glass fibers prepared by cutting theglass fibers obtained in Material 4 into a length of 6 mm with acartridge cutter instead of chopped carbon fibers. The basis weight ofthe glass fiber base material was 100 g/m². The properties of the glassfiber base material are shown in Table 7.

A prepreg (19) composed of the glass fiber base material impregnatedwith Nylon 6 resin was produced in the same manner as in Example 1,except for using the above-mentioned glass fiber base material. Theproperties of the prepreg are shown in Table 8.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which nineteenprepregs (19) had been laminated. The preform was shaped well inconformity with the shape of the mold and a molded product that was highin shape quality was obtained. The properties of the molded product areshown in Table 9.

Example 18

A prepreg (20) was produced in the same manner as in Example 2, exceptfor using chopped carbon fibers prepared by cutting the carbon fibersobtained in Material 2 into a length of 6 mm with a cartridge cutter aschopped carbon fibers. The properties of the prepreg are shown in Table8.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which seventeenprepregs (20) had been laminated. The preform was shaped well inconformity with the shape of the mold and a molded product that was highin shape quality was obtained. The properties of the molded product areshown in Table 9.

Example 19

A prepreg (21) was produced in the same manner as in Example 14 exceptthat the PP resin film with which the carbon fiber base material was tobe impregnated was adjusted so that the fiber mass content might become40%. The properties of the prepreg are shown in Table 8.

An L-shaped box-like molded product was produced in the same manner asin Example 14 except for manufacturing a preform in which seventeenprepregs (21) had been laminated. The preform was shaped well inconformity with the shape of the mold and a molded product that was highin shape quality was obtained. The properties of the molded product areshown in Table 9.

Example 20

A laminated preform (A) was prepared by laminating eight prepregs (1)and then the preform (A) was pressurized at a temperature of 250° C. for1 minute under a pressure of 5 MPa, so that a preform (B) in which theprepregs (1) had been adhered to each other was produced. The propertiesof the preform are shown in Table 10.

Using this preform (B), an L-shaped box-like molded product of a B5 sizewas produced in the same manner as in Example 1. Since the prepregs (1)had been adhered together, the standing wall portion of the L-shapedbox-like molded product was a little thin and the surface thereof wasroughened a little, so that the shapeability was a little poor, but themolded product was capable of being used. The properties of the moldedproduct are shown in Table 10.

Example 21

A laminated preform (C) was produced by laminating the prepregs (1) andthe prepregs (2), eight sheets in total, in a constitution of[(2)/(1)×6/(2)]. The properties of the preform are shown in Table 10.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 10.

Example 22

A laminated preform (D) was produced by laminating the prepregs (1) andthe prepregs (20), eight sheets in total, in a constitution of[(20)/(1)×6/(20)]. The properties of the preform are shown in Table 10.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 10.

Example 23

A laminated preform (E) was produced by laminating the prepregs (1) andthe prepregs (19), six sheets in total, in a constitution of[(1)/(19)×4/(1)]. The properties of the preform are shown in Table 10.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 10.

Example 24

A laminated preform (F) was produced by laminating the prepregs (1) andTORAYCA prepreg of Material 10, eight sheets in total, in a constitutionof [TORAYCA prepreg/(1)×7]. The properties of the preform are shown inTable 10. Here, the TORAYCA prepreg is arranged so that the top panelportion of the molded product of FIG. 5 may be reinforced.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 10.

Example 25

A laminated preform (G) was produced by laminating the prepregs (1) andGMT of Material 5, three sheets in total, in a constitution of[(1)/GMT/(1)]. The properties of the preform are shown in Table 11.Here, the prepreg (1) and the GMT were arranged so that the charge ratiomight be 110% for the prepreg (1) and 50% for GMT as illustrated in FIG.6.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 11.

Example 26

A laminated preform (H) was produced by laminating the prepregs (21) anda PP resin sheet of Material 6, three sheets in total, in a constitutionof [(21)/PP resin sheet/(21)]. The properties of the preform are shownin Table 11.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 11.

Example 27

A laminated preform (I) was produced by laminating the prepregs (21) anda foamed PP resin sheet of Material 7, three sheets in total, in aconstitution of [(21)/foamed PP resin sheet/(21)]. The properties of thepreform are shown in Table 11.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 11.

Example 28

A laminated preform (J) was produced by laminating the prepregs (1) anda transparent Nylon resin film of Material 8, nine sheets in total, in aconstitution of [transparent Nylon resin sheet/(1)×8]. The properties ofthe preform are shown in Table 11.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. Since the surfacewas the transparent Nylon resin sheet, it was glossy and it providedluxuriousness. The properties of the molded product are shown in Table11.

Example 29

A laminated preform (K) was produced by laminating the prepregs (1) anda Nylon resin flame retardant film of Material 9, nine sheets in total,in a constitution of [Nylon resin flame retardant film/(1)×8]. Theproperties of the preform are shown in Table 11.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using this preform. The molded product wasshaped well in conformity with the shape of the mold and a moldedproduct that was high in shape quality was obtained. The properties ofthe molded product are shown in Table 11. Moreover, the height of aflame of a burner was adjusted to 19 mm and flame retardancy measurementcomprising exposing the surface of the molded product where the Nylonresin flame retardant film had been disposed to the flame and 5 secondslater removing it from the flame. The flame went out after the removalfrom the flame.

Example 30

An L-shaped box-like molded product was produced in the same manner asin Example 1, except for exchanging the stamping mold which had anL-shaped box-like cavity of the B5 size to a mold having a stamping-outmechanism for stamping-out an excess portion of located at an edge ofthe molded product. The process was shortened successfully by performingmolding and stamping-out simultaneously.

Comparative Example 1

A carbon fiber base material was produced in the same manner as inExample 1 except for adjusting the basis weight of the carbon fiber basematerial to 410 g/m² by adjusting the flow rate of the dispersion liquidand the speed of the mesh conveyer during papermaking. The properties ofthe carbon fiber base material are shown in Table 12. The Nylon 6 resinfilm with which this carbon fiber base material was to be impregnatedwas adjusted so that the fiber mass content might become 20% and apressure of 5 MPa was applied at a temperature of 250° C. for twominutes, so that a prepreg (22) in which the carbon fiber base materialhad been impregnated with the Nylon 6 resin was produced. The propertiesof the prepreg are shown in Table 13.

An L-shaped box-liked molded product was produced in the same manner asin Example 1 except for using one prepreg (22) as a preform. It wasdifficult to shape the preform in conformity with the shape of the mold,so that the standing wall portion failed to be uniform in thickness andit was partly torn. The properties of the molded product are shown inTable 15.

Comparative Example 2

A prepreg (23) in which carbon fibers and Nylon 6 fibers had been mixedwas obtained by performing papermaking in the same manner as in Example1, except for charging, into a dispersion liquid, the chopped carbonfibers used in Example 1 and Nylon 6 resin chopped fibers of Material 15in a formulation such that the fiber mass content might become 20%. Theproperties of the prepreg are shown in Table 13. The basis weight ofonly the carbon fibers was 50 g/m². Although molding of a bonnet for anautomobile was attempted in the same manner as in Example 16, except forusing the prepreg (23), the prepreg (23) was ruptured duringtransportation, lamination, and movement in manufacturing a preform inwhich 24 prepregs (23) had been laminated because the tensile strengthof the prepreg (23) was low, so that it could not be molded.

Comparative Example 3

An L-shaped box-like molded product was produced in the same manner asin Example 1, except for using one sheet of GMT (prepreg (24)) ofMaterial 5 and arranging it at a charge ratio of 50%. Since the GMT wasexcessively thick, it was not able to be molded into a molded product of1.1 mm in thickness and no satisfactory molded product with a desiredthickness was obtained. The properties of the molded product are shownin Table 14.

Comparative Example 4

An L-shaped box-like molded product was produced in the same manner asin Example 13, except for using one sheet of CF-SMC (prepreg (25)) ofMaterial 11 and arranging it at a charge ratio of 50%. Although themolded product was shaped well in conformity with the shape of the moldand the molded product that was high in shape quality was obtained, thearticle was low in specific strength and poor in isotropy because thecarbon fibers were dispersed in a bundle form. The properties of themolded product are shown in Table 14.

Comparative Example 5

A preform of quasi-isotropic lamination [0/45/90/−45]s was producedusing eight sheets of cut-in carbon fiber prepregs (prepregs (26)) ofMaterial 12, and an L-shaped box-like molded product was produced in thesame manner as in Example 13. Although the molded product was shapedwell in conformity with the shape of the mold and the molded productthat was high in shape quality was obtained, the article was poor inisotropy because the carbon fibers were dispersed in a bundle form. Theproperties of the molded product are shown in Table 14.

Comparative Example 6

A preform of quasi-isotropic lamination [0/45/90/−45]s was producedusing eight sheets of TORAYCA prepregs (prepregs (27)) of Material 10,and an L-shaped box-like molded product was produced in the same manneras in Example 13, but it was difficult to provide a shape and a standingwall, corner portions and so on were not capable of being shaped becausethe carbon fibers were continuous.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Example 7 Reinforcing Reinforcing Kind of fiber [—] Carbon Carbon CarbonCarbon Carbon Carbon Carbon fiber base fiber fiber 1 fiber 1 fiber 1fiber 1 fiber 1 fiber 1 fiber 1 material Fiber mass content [% by mass]28 52 65 15 8 28 28 Fiber Longer [% by mass] 0 0 0 0 0 0 0 length thanProportion 10 mm 2 to [% by mass] 95 95 95 95 95 95 95 10 mm Shorter [%by mass] 5 5 5 5 5 5 5 than 2 mm Two-dimensional orientation angle [°]40 42 41 40 40 25 40 Amount of air (Frazier method) [cm³/cm² · s] 160160 150 160 160 160 450

TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Example 7 Prepreg Prepreg number [—]  (1)  (2)  (3)  (4)  (5)  (6)  (7)Resin Kind of resin [—] Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6Nylon 6 Resin mass content [% by mass]  72  48  35  85 92  72  72Feature Thickness at 23° C., hp0 [mm]    0.15    0.07    0.07    0.28   0.56    0.15    0.06 Thickness at 100° C., h1 [mm]    0.15    0.07   0.07    0.28    0.56    0.15    0.06 Thickness at 200° C., h2 [mm]   0.18    0.10    0.11    0.30    0.58    0.18    0.08 Thickness at300° C., h3 [mm]    0.92    0.45    0.49    0.85    0.73    0.92    0.46(*2) (*2) (*2) (*2) (*2) (*2) (*2) Thickness at 400° C., h4 [mm] (*1)(*1) (*1) (*1) (*1) (*1) (*1) Resin impregnation ratio [%]  95  95  95 99 99  95  95 Bulk density [g/cm³]    1.20    1.33    1.46    1.19   1.15    1.20    1.20 Mass per unit area [g/m²] 180 100 100 330 650 180  35 Tensile strength σ [MPa] 150 200 210 120  90 150 120 σMax [MPa]170 220 220 135 95 200 130 σMim [MPa] 140 185 190 110 85 120 105 Lengthin the longitudinal [mm] 500 500 500 500 500  500 500 direction (*1):Resin was decomposed. (*2): Resin was slightly decomposed.

TABLE 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Example 7 Molded Molding method Stamping Stamping Stamping StampingStamping Stamping Stamping product Properties Specific strength B A A BC B B Isotropy A A A A A B A Specific rigidity B B B B C B B Isotropy AA A A A B A Coefficient of linear expansion A A A C D A A Isotropy A A AA A A A

TABLE 4 Exam- Example Exam- Example 8 Example 9 Example 10 Example 11ple 12 13 ple 14 Reinforcing Reinforcing Kind of fiber [—] Carbon CarbonCarbon Carbon Carbon Carbon Carbon fiber base fiber fiber 1 fiber 1fiber 1 fiber 1 fiber 1 fiber 1 fiber 1 material There are Carbon twopeaks fiber 2 of fiber There are length two peaks distribution. of fiberlength distribution. Fiber mass content [% by mass] 28 28 28 52 28 25 33Fiber Longer [% by mass] 0 0 0 0 0 0 0 length than Proportion 10 mm 2 to10 [% by mass] 95 95 95 95 95 95 95 mm Shorter [% by mass] 5 5 5 5 5 5 5than 2 mm Two-dimensional orientation angle [°] 40 40 40 40 40 40 40Amount of air (Frazier method) [cm³/cm² · s] 1100 80 200 180 160 160 160

TABLE 5 Example Example Example Example 8 Example 9 Example 10 Example11 12 13 14 Prepreg Prepreg number [—]  (8)  (9)  (10)  (11) (12)  (13) (14) Resin Kind of resin [—] Nylon 6 Nylon 6 Nylon 6 Nylon 6 Nylon 6PPS PP Resin mass content [% by mass]  72  72  72  48 72  75  67 FeatureThickness at 23° C., hp0 [mm]    0.03    0.58    0.15    0.07    0.69   0.15    0.15 Thickness at 100° C., h1 [mm]    0.03    0.58    0.15   0.07    0.69    0.15    0.15 Thickness at 200° C., h2 [mm]    0.04   0.62    0.16    0.08    0.73    0.15    0.69 Thickness at 300° C., h3[mm]    0.18    3.45    0.73    0.36    0.95    0.88 (*1) (*2) (*2) (*2)(*2) (*2) Thickness at 400° C., h4 [mm] (*1) (*1) (*1) (*1) (*1)    0.94(*1) (*2) Resin impregnation ratio [%]  95  95  95  95 20  95  95 Bulkdensity [g/cm³]    1.20    1.25    1.20    1.33    0.25    1.37    1.03Mass per unit area [g/m²]  35 620 180 100 180  200 150 Tensile strengthσ [MPa] 120 160 140 180 60 145 120 σMax [MPa] 130 175 155 200 70 155 130σMim [MPa] 105 150 130 165 65 140 115 Length in the longitudinal [mm]500 500 500 500 500  500 500 direction (*1): Resin was decomposed. (*2):Resin was slightly decomposed.

TABLE 6 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13Example 14 Molded Molding method Stamping Stamping Stamping StampingStamping Stamping Stamping product Properties Specific strength B B B AB B B Isotropy A A AA AA A A A Specific rigidity B B B A B B B IsotropyA A AA AA A A A Coefficient of linear expansion A A A A A A A Isotropy AA A A A A A

TABLE 7 Referential Referential Example Example Exam- Example Exam-Example 1 Example 2 15 16 ple 17 18 ple 19 Reinforcing Reinforcing Kindof fiber [—] Carbon Carbon Carbon Carbon Grass Carbon Carbon fiber basefiber fiber 1 fiber 1 fiber 1 fiber 1 fiber fiber 2 fiber 1 materialFiber mass content [% by mass] 27 27 28 28 36 52 57 Fiber Longer [% bymass] 0 0 0 0 0 0 0 length than Proportion 10 mm 2 to [% by mass] 95 9595 95 95 95 95 10 mm Shorter [% by mass] 5 5 5 5 5 5 5 than 2 mmTwo-dimensional orientation angle [°] 40 40 40 40 40 40 40 Amount of air(Frazier method) [cm³/cm² · s] 160 160 160 160 250 160 160

TABLE 8 Referential Referential Example Example Example Example ExampleExample 1 Example 2 15 16 17 18 19 Prepreg Prepreg number [—] (15)   (16)     (17)  (18)  (19)  (20)  (21) Resin Kind of resin [—] EpoxyEpoxy Nylon 6 Nylon 6 Nylon 6 Nylon 6 PP uncured uncured 10 wt % red Tgviscosity Tg viscosity phosphorus is low. is high. acid wasincorporated. Resin mass content [% by mass] 73    73     72  72  64  48 43 Feature Thickness at 23° C., hp0 [mm] 0.15 0.15    0.15    0.15   0.21    0.07    0.07 Thickness at 100° C., h1 [mm] 0.75 0.35    0.15   0.15    0.21    0.07    0.07 Thickness at 200° C., h2 [mm] 0.82 0.55   0.17    0.18    0.22    0.09    0.35 Thickness at 300° C., h3 [mm](*1) (*1)    0.88    0.92    0.83    0.58 (*1) (*2) (*2) (*2) (*2)Thickness at 400° C., h4 [mm] (*1) (*1) (*1) (*1) (*1) (*1) (*1) Resinimpregnation ratio [%] 95    95     95  95  95  95  95 Bulk density[g/cm³] 1.25 1.25    1.22    1.20    1.33    1.33    1.20 Mass per unitarea [g/m²] 180    180    180 180 280 100  90 Tensile strength σ [MPa]0.05 0.1  160 150 110 140 135 σMax [MPa] 0.06 0.11 175 170 120 150 145σMim [MPa] 0.04 0.09 150 140 105 130 125 Length in the [mm] 500   500    500 1500  500 500 500 longitudinal direction (*1): Resin wasdecomposed. (*2): Resin was slightly decomposed.

TABLE 9 Referential Referential Example Example Example 1 Example 2Example 15 16 Example 17 Example 18 19 Molded Molding method Heat pressHeat press Stamping Stamping Stamping Stamping Stamping productProperties Specific strength B B B B C A B Isotropy A A A A A A ASpecific rigidity B B B B C A A Isotropy A A A A A A A Coefficient oflinear expansion A A A A C A A Isotropy A A A A A A A

TABLE 10 Example 1 Example 20 Example 21 Example 22 Example 23 Example24 Preform Preform number [—] (A) (B) (C) (D) (E) (F) Used prepregPrepreg number [—] (1)   (1)   (1), (2) (1), (20) (1), (19) (1),Continuous CFRTP Laminated [—] Eight-sheet Eight-sheet (2)/(1) × 6/(2)(20)/(1) × (1)/(19) × Core layer configuration lamination lamination6/(20) 4/(1) (1) × 7 Single-side continuous CFRTP Feature Thickness at23° C., hp0 [mm] 1.2 1.2 1.1 1.1 1.1 1.2 Thickness at 100° C., h1 [mm]1.3 1.2 1.2 1.2 1.2 1.3 Thickness at 200° C., h2 [mm] 1.5 1.4 1.5 1.51.4 1.4 Thickness at 300° C., h3 [mm] 7.9 7.9 8.2 8.1 6.3 7.5 (*2) (*2)(*2) (*2) (*2) (*2) Thickness at 400° C., h4 [mm] (*1) (*1) (*1) (*1)(*1) (*1) Interlayer shear strength [MPa] 0   60   0   0   0   0  Molded Molding method Stamping Stamping Stamping Stamping StampingStamping product Properties Specific strength [—] B B B B C A Isotropy[—] A A A A A B Specific rigidity [—] B B A A C A Isotropy [—] A A A A AB Coefficient of linear [—] B B A A B A expansion Isotropy [—] A A A A AB (*1): Resin was decomposed. (*2): Resin was slightly decomposed.

TABLE 11 Example 25 Example 26 Example 27 Example 28 Example 29 Example30 Preform Preform number [—] (G) (H) (I) (J) (K) (A) Used prepregPrepreg number [—] (14), GMT (21), PP (21), foamed (1), surfacing (1),flame (1)   resin sheet sheet film retardant film Laminated [—] (14)/(21)/resin (21)/foamed surfacing film/ flame retardant Eight-sheetconfiguration GMT/(14) sheet/(21) sheet/(21) (1) × 8 film/(1) × 8lamination Feature Thickness at 23° C., hp0 [mm] 4.1 1.2 1.2 1.3 1.3 1.2Thickness at 100° C., h1 [mm] 4.1 1.2 1.2 1.3 1.3 1.3 Thickness at 200°C., h2 [mm] 15.4  1.9 2.1 1.4 1.4 1.5 Thickness at 300° C., h3 [mm] (*1)(*1) (*1) 8.1 8.1 7.9 (*2) (*2) (*2) Thickness at 400° C., h4 [mm] (*1)(*1) (*1) (*1) (*1) (*1) Interlayer shear strength [MPa] 0   0   0   0  0   0   Molded Molding method Stamping Stamping Stamping StampingStamping Stamping + product punching Properties Specific strength [—] CB B B B B Isotropy [—] A A A A A A Specific rigidity [—] B AA AAA B B BIsotropy [—] A A A A A A Coefficient of linear [—] B A A B B B expansionIsotropy [—] A A A A A A (*1): Resin was decomposed. (*2): Resin wasslightly decomposed.

TABLE 12 Compar- Compar- ative ative Comparative Comparative ComparativeComparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Reinforcing Reinforcing Kind of fiber [—] Carbon Carbon Grass CarbonCarbon Carbon fiber base fiber fiber 1 fiber 1 fiber fiber 3 fiber fibermaterial Fiber mass content [% by mass] 28 28 40 60 67 67 Fiber Longerthan [% by mass] 0 0 95 100 100 100 length 10 mm Proportion 2 to 10 mm[% by mass] 95 95 5 0 0 0 Shorter than [% by mass] 5 5 0 0 0 0 2 mmTwo-dimensional orientation angle [°] 40 40 30 2 1 1 Amount of air(Frazier method) [cm³/cm² · s] 40 160 60 40 15 10

TABLE 13 Comparative Comparative Comparative Comparative ComparativeComparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Prepreg Prepreg number [—]  (22) (23)    (24) (25)   (26)   (27)   ResinKnd of resin [—] Nylon 6 Epoxy PP Vinyl ester Epoxy Epoxy Resin masscontent [% by  72 72    60 40   33   33   mass] Feature Thickness at 23°C., hp0 [mm]    1.2 0.95   3.8 2.0  0.15  0.15 Thickness at 100° C., h1[mm]    1.2 0.95   3.8 2.0  0.15  0.15 Thickness at 200° C., h2 [mm]   1.3 0.96   14.1 2.1  0.16  0.16 Thickness at 300° C., h3 [mm]    0.840.98 (*1) (*1) (*1) (*1) (*2) (*2) Thickness at 400° C., h4 [mm] (*1)(*1) (*1) (*1) (*1) (*1) Resin impregnation ratio [%]  95 0   70 95  95   95   (Resin fiber mixing) Bulk density [g/cm³]    1.20 1.90    1.24 1.20  1.47  1.47 Mass per unit area [g/m²] 1440  180    3900  3900   220    220    Tensile strength σ [MPa] 250  0.005 30 0.3  0.01 200   σMax [MPa] 255  0.006 35 0.4 0.5 1000    σMim [MPa] 235  0.004 20  0.25 0.005  0.005 Length in the longitudinal direction [mm] 500 1500    500  500    1000    1000    (*1): Resin was decomposed. (*2): Resin wasslightly decomposed.

TABLE 14 Comparative Comparative Comparative Comparative ComparativeComparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Molded Molding method Stamping — Stamping Heat press Heat press Heatpress product Properties Specific strength B — D D B — Isotropy A — C CC — Specific rigidity B — C B A — Isotropy A — C C C — Coefficient oflinear A — D A A A expansion Isotropy A — C C C C

As demonstrated in Examples 1 to 19, the isotropic prepregs which weregood in distribution of the fiber length of reinforcing fibers,thickness and tensile strength and in which the two-dimensionalorientation angle of fibers was from 10 to 80° exhibited good propertieswhen a molded product was produced therefrom. In addition, the laminatedpreforms of Example 1 and Examples 20 to 30 produced using theseprepregs also demonstrated good properties.

On the other hand, in Comparative Example 1, which was a prepreg with agreat thickness was difficult to be shaped and it generated defectspartly in the molded product. Moreover, in Comparative Example 2 using aprepreg which was low in tensile strength, rupture occurred during theManufacture of a preform. Furthermore, in Comparative Example 3 usingGMT, the thickness was large, so that it was very difficult to performthin-wall molding. The isotropy of mechanical properties was also poorbecause of the occurrence of flow. In Comparative Example 4 usingCF-SMC, the two-dimensional orientation angle of the fibers was small,and the mechanical properties and their isotropy were poor. InComparative Example 5 using a cut-in carbon fiber prepreg, mechanicalproperties were improved, but the isotropy was still poor because thefibers were in the form of a bundle. Comparative Example 6, in which acontinuous fiber prepreg was used, was difficult to complete a shape.

[Evaluation of Method for Manufacturing Prepreg]

Raw materials used for Examples

(Carbon Fiber A1) Pan Type Carbon Fiber

Carbon fiber A1 was produced as follows.

An acrylic fiber bundle having a filament denier of 1 d and the numberof filaments of 12,000 was obtained by the dry-wet type spinning processusing a copolymer composed of 99.4 mol % of acrylonitrile (AN) and 0.6mol % of methacrylic acid. The resulting acrylic fiber bundle was heatedin a draw ratio of 1.05 in the air of a temperature of from 240 to 280°C. to convert it to flame-resistant fibers, and then 10% draw wasapplied in a nitrogen atmosphere within a temperature range of from 300to 900° C. at a temperature elevation rate of 200° C./min, followed bycalcination with a temperature elevation up to 1300° C. The carbon fiberbundle was subjected to electrolytic surface treatment of 3 coulombs pergram of the carbon fibers using an aqueous solution containing sulfuricacid as an electrolyte. Furthermore, a sizing agent was imparted by adipping process and then dried in hot air at a temperature of 120° C.,yielding PAN type carbon fibers.

Total number of filaments 24,000 Filament diameter 7 μm Mass per unitlength 0.8 g/m Specific gravity 1.8 g/cm³ Tensile strength (Note 1) 4.2GPa Tensile modulus (Note 2) 230 GPa O/C (Note 3) 0.10 Kind of sizingPolyoxyethylene oleyl ether Amount of attached sizing (Note 4) 1.5% bymass

(Carbon Fiber A2) Pan Type Carbon Fiber

Carbon fiber A2 was produced as follows. An acrylic fiber bundle havinga filament denier of 1 d and the number of filaments of 12,000 wasobtained by the dry-wet type spinning process using a copolymer composedof 99.4 mol % of acrylonitrile (AN) and 0.6 mol % of methacrylic acid.The resulting acrylic fiber bundle was heated in a draw ratio of 1.05 inthe air of a temperature of from 240 to 280° C. to convert it toflame-resistant fibers, and then 10% draw was applied in a nitrogenatmosphere within a temperature range of from 300 to 900° C. at atemperature elevation rate of 200° C./min, followed by calcination witha temperature elevation up to 1300° C. Furthermore, a sizing agent wasimparted by a dipping process and then dried in hot air at a temperatureof 120° C., yielding PAN type carbon fibers.

Total number of filaments 12,000 Filament diameter 7 μm Mass per unitlength 0.8 g/m Specific gravity 1.8 g/cm³ Tensile strength (Note 1) 4.2GPa Tensile modulus (Note 2) 230 GPa O/C (Note 3) 0.05 Kind of sizingPolyoxyethylene oleyl ether Amount of attached sizing (Note 4) 0.6% bymass

(Carbon Fiber A3) Pan Type Carbon Fiber

Carbon fiber A3 was produced as follows. An acrylic fiber bundle havinga filament denier of 1 d and the number of filaments of 12,000 wasobtained by the dry-wet type spinning process using a copolymer composedof 99.4 mol % of acrylonitrile (AN) and 0.6 mol % of methacrylic acid.The resulting acrylic fiber bundle was heated in a draw ratio of 1.05 inthe air of a temperature of from 240 to 280° C. to convert it toflame-resistant fibers, and then 10% draw was applied in a nitrogenatmosphere within a temperature range of from 300 to 900° C. at atemperature elevation rate of 200° C./min, followed by calcination witha temperature elevation up to 1300° C. Furthermore, a sizing agent wasimparted by a dipping process and then dried in hot air at a temperatureof 120° C., yielding PAN type carbon fibers.

Total number of filaments 48,000 Filament diameter 7 μm Mass per unitlength 0.8 g/m Specific gravity 1.8 g/cm³ Tensile strength (Note 1) 4.2GPa Tensile modulus (Note 2) 230 GPa O/C (Note 3) 0.05 Kind of sizingPolyoxyethylene oleyl ether Amount of attached sizing (Note 4) 1.5% bymass

(Matrix Resin B1) Acid-Modified Polypropylene Resin

As matrix resin B1 was used “ADMER” (registered trademark) QE510,manufactured by Mitsui Chemicals, Inc. The physical properties are asfollows.

Specific gravity 0.91 Melting point 160° C.

(Matrix Resin B2) Nylon 6 Resin

As matrix resin B2 was used “Amilan” (registered trademark) CM1001,manufactured by Toray Industries, Inc. The physical properties are asfollows.

Specific gravity 1.13 Melting point 225° C.

(Matrix Resin B2) PPS Resin

As matrix resin B3 was used “Torelina” (registered trademark) A900,manufactured by Toray Industries, Inc. The physical properties are asfollows.

Specific gravity 1.34 Melting point 278° C.

(Matrix Resin B4) Epoxy Resin

Thirty parts by mass of “EPICOAT” (registered trademark) 828 (bisphenolA type epoxy resin, produced by Japan Epoxy Resins Co., Ltd.), 30 partsby mass of “EPICOAT” (registered trademark) 1002 (bisphenol A type epoxyresin, produced by Japan Epoxy Resins Co., Ltd.), 40 parts by mass of“EPICOAT” (registered trademark) 154 (phenol novolac type epoxy resin,produced by Japan Epoxy Resins Co., Ltd.), 5 parts by mass of “VINYLEC”(registered trademark) (polyvinyl formal, produced by Chisso Corp.), 4parts by mass of DICY7 (dicyandiamide, produced by Japan Epoxy ResinsCo., Ltd.), and 5 parts by mass of DCMU-99(3,4-dichlorophenyl-1,1-dimethylurea, produced by Hodogaya Chemical Co.,Ltd.) were mixed with a kneader in the following procedures, yielding anepoxy resin composition in which the polyvinyl formal had been dissolveduniformly.

(a) Respective epoxy resin raw materials and polyvinyl formal werestirred for 1 to 3 hours homogeneously while being heated at 150 to 190°C., so that the polyvinyl formal was dissolved.(b) The resin temperature was lowered to 55 to 65° C., and thendicyandiamide and 3-(3,4-dichlorophenyl)-1,1-dimethylurea were added,kneaded at that temperature for 30 to 40 minutes, and then taken outfrom the kneader, so that a resin composition was obtained.

(Binder Component C1)

As a binder component constituting a binder was used “POLYMENT”(registered trademark) SK-1000 produced by NIPPON SHOKUBAI Co., Ltd. Itsmain constituent is an acrylic polymer that has an aminoalkylene groupin a side chain.

(Binder Component C2)

As a binder component constituting a binder was used “EPOCROS”(registered trademark) WS-700 produced by NIPPON SHOKUBAI Co., Ltd. Itsmain constituent is an acrylic polymer that has an oxazoline group in aside chain.

Conditions for Measuring Tensile Strength (Note 1) and Tensile Modulus(Note 2)

The determination was done by using the procedures described in JapaneseIndustrial Standard (JIS) R-7601 “Testing method for strands impregnatedwith resin.” Strands impregnated with resin of the carbon fiber to bemeasured were formed by impregnating the carbon fiber with “BAKELITE”(registered trademark) ERL4221 (100 parts by mass)/boron trifluoridemonoethylamine (3 parts by mass)/acetone (4 parts by mass) and thencuring them at 130° C. for 30 minutes. The number of the strands to bemeasured was determined to be six and the averages of the respectivemeasurement results were defined as the tensile strength and the tensilemodulus of the carbon fiber.

(Note 3) Measurement Condition of Measurement of O/C

The determination was done in the following procedures by X-rayphotoelectron spectroscopy. First, carbon fibers from the surface ofwhich adherents or the like had been removed were cut into 20 mm andthen spread and arranged on a copper sample support. Then, the inside ofa sample chamber was held at 1×10⁹ Torr by the use of A1Kα1, 2 as anX-ray source. The kinetic energy value (K.E.) of the primary peak ofC_(1s) was adjusted to 1202 eV as a correction value of a peakaccompanying the electrification at the time of measurement. The area ofthe C_(1s) peak was determined by drawing a straight baseline within arange of from 1191 to 1205 eV in K.E. The area of the O_(1s) peak wasdetermined by drawing a straight baseline within a range of from 947 to959 eV in K.E.

The surface oxygen concentration was calculated as an atomic numberratio from the ratio of the O_(1s) peak area and the C_(1s) peak areausing a sensitivity correction value that was inherent to an instrument.Model ES-200 manufactured by International Electric Co., Ltd., was usedas an X-ray photoelectron spectrometer, and the sensitivity correctionvalue was determined to be 1.74.

(Note 4) Measurement Condition of Amount of Attached Sizing Agent

About 5 g of carbon fibers to which a sizing agent had attached weretaken as a sample and then were charged into a heat-resistant container.Next, this container was dried at 120° C. for 3 hours. After cooling toroom temperature in a desiccator with care not to allow moistureabsorption, the mass was measured, which was determined as W₁ (g).Subsequently, the sample was heated together with the container in anitrogen atmosphere at 450° C. for 15 minutes and then cooled to roomtemperature in a desiccator with care not to allow moisture absorption,and then the mass was measured, which was determined as W₂ (g). Throughthe above treatments, the amount of the sizing agent attaching to thecarbon fibers was determined by using the following formula.

Attached amount (% by mass)=100×{(W₁−W₂)/W₂}  (Formula)

The measurement was conducted three times and the average thereof wasadopted as an attached amount.

The criteria of evaluations of the carbon fiber base materials to beobtained in each Example are as follows.

(21) Total Process Time

The time taken from the steps (I) to (III) and the time taken from thesteps (I) to (IV) were measured.

(22) Evaluation of Dispersion State of Reinforcing Fibers

A web was cut out in a square shape with a size of 50 mm×50 mm from anarbitrary part of the reinforcing fiber base material produced in thestep (I) and it was observed with a microscope. Then, a state that tenor more carbon filament formed a bundle, that is, the number of bundlesof carbon fibers with insufficient dispersion was measured. Measurementwas conducted 20 times in this procedure and an average was calculated.Then, evaluation was done on the basis of the following criteria.

AA: There is less than one carbon fiber bundle with insufficientdispersion.

A: There are one or more and less than five carbon fiber bundles withinsufficient dispersion.

B: There are five or more and less than ten carbon fiber bundles withinsufficient dispersion.

C: There are ten or more carbon fiber bundles with insufficientdispersion.

(23) Handling Performance of Prepreg

The handling performance of a prepreg obtained was evaluated on thebasis of the following criteria.

A: A carbon fiber base material and a matrix resin are integratedtogether and the handling performance is good.

B: A carbon fiber base material and a matrix resin are separated fromeach other and cautions are required for handling.

(24) Evaluation of the Mechanical Properties of a Molded Product

A resulting prepreg was cut into 200 mm×200 mm and was dried at 120° C.for one hour. A molded product with a thickness of 1.0 mm was preparedby laminating eight prepregs after drying, press molding the laminateunder a pressure of 30 MPa for five minutes, and cooling it to 50° C.while maintaining the pressure. By using the resulting molded product,flexural strength was evaluated at n=10 in accordance with the ISO178method (1993). An evaluation result of the flexural strength wasexpressed in a relative value on an Example 1 base material of 100. Thevariation of the evaluation results was expressed in a coefficient ofvariation (CV value).

Example 101 Manufacture of Prepreg P1 by Wet Process

A prepreg P1 was produced by using an apparatus 101 of FIG. 9. Theapparatus 101 is composed of a dispersion vessel 111, a papermakingvessel 112, and a binder vessel 126. The dispersion vessel 111 is acontainer in a cylindrical form of 300 mm in diameter and has a slurrytransport portion 113 with an opening cock 115 at a lower portion of thecontainer. As the papermaking vessel 112 is used a large-sizedsquare-shaped sheet machine (No. 2553-I (commercial name), manufacturedby Kumagai Riki Kogyo Co., Ltd.). The binder vessel 126 has a bindertransport portion 127 with an opening cock 128 at a lower portion of thevessel. The opening of the binder transport portion 127 is located abovethe papermaking vessel 112. The binder transport portion 127 is movableand can sprinkle a binder uniformly on a reinforcing fiber base material120. A stirrer 116 is mounted to the upper opening of the dispersionvessel 111 and a carbon fiber bundle 117 and a dispersion medium 118 canbe charged through the opening. The bottom of the papermaking vessel 12has a papermaking surface 119 (made of mesh sheet) of 400 mm in lengthand 400 mm in width, and a reinforcing fiber base material 120 is formedon the papermaking surface 119.

Carbon fiber A1 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber (A1-1) was obtained. A 1%-by-mass aqueousdispersion liquid (emulsion) of C1 had been produced as a bindersolution and put into a binder vessel 126. Twenty liters of a dispersionliquid with a concentration of 0.1% by mass composed of water and asurfactant (polyoxyethylene lauryl ether (commercial name), produced byNacalai Tesque, Inc.) was prepared and transferred to a dispersionvessel 111. 9.6 g of A1-1 (chopped carbon fiber) was added to thisdispersion liquid, followed by stirring for 10 minutes. Thus, a slurrywas prepared. The opening cock 115 provided at the lower portion of thedispersion vessel was opened to pour the slurry into the papermakingvessel 112 and then water was aspirated to yield a carbon fiber basematerial of 400 mm in length and 400 mm in width (step (I)).Subsequently, an opening cock 128 of the binder vessel 126 was openedand 200 g of the binder solution was sprinkled from the upper side ofthe carbon fiber base material. An excess of the binder solution wasaspirated, yielding a carbon fiber base material 120 to which a bindersolution had been imparted. The carbon fiber base material 120 was takenout from the manufacture apparatus 101 and was dried at 150° C. for 20minutes, yielding a carbon fiber base material W1 (step (II)). The basisweight of the carbon fiber base material W1 was 60 g/m². A non-wovenfabric of B1 (resin basis weight: 30 g/m²) was arranged as a matrixresin on both sides of the carbon fiber base material W1 and then waspressurized at 220° C., 10 MPa, yielding a prepreg P1 in which thecarbon fiber base material had been impregnated with the matrix resin(step (III)). The execution conditions of the respective steps and theevaluation results of the resulting prepreg are shown in Table 15.

Example 102 Manufacture of Prepreg P2 by Wet Process

A prepreg was produced by using an apparatus 102 of FIG. 10. Theapparatus 102 is composed of a dispersion layer 111, a papermakingvessel 112, a binder vessel 126, a conveyor 122, a dryer 138, a doublebelt press 131, and a winding machine 133. The dispersion vessel 111 isa container in a cylindrical form of 300 mm in diameter and has a slurrytransport portion 113 with an opening cock 115 at a lower portion of thecontainer, and a pressurized air tube 129 for supplying pressurized airinto the vessel. The binder vessel 126 is provided with a bindertransport portion 127 with an opening cock 128 at a lower portion of acontainer, and a pressurized air tube 130 for supplying pressurized airinto the vessel. The papermaking vessel 112 has, at its bottom, a meshconveyor 121 with a papermaking surface 119 having a width of 200 mm.The conveyor 122 is disposed following a mesh conveyor 121 and conveys areinforcing fiber base material. The opening of the binder transportportion 127 is located above the conveyor 122. The dryer 138 dries thereinforcing fiber base material 120 on the conveyor 122. The double beltpress 131 horizontally introduces the reinforcing fiber base material120 conveyed by the conveyor 122. To the double belt press 131 arecharged, together with the reinforcing fiber base material 120, a matrixresin 135 toward both sides of the reinforcing fiber base material 120from rolls 136,137. The winding machine 133 winds the resulting prepreg132.

Carbon fiber A1 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber (A1-1) was obtained.

A 1%-by-mass aqueous dispersion liquid (emulsion) of C1 had beenproduced as a binder solution and put into a binder vessel 126. Fortyliters of a dispersion liquid with a concentration of 0.1% by masscomposed of water and a surfactant (polyoxyethylene lauryl ether(commercial name), produced by Nacalai Tesque, Inc.) was prepared andtransferred to a dispersion vessel 111. 20 g of A1-1 (chopped carbonfiber) was added to this dispersion-liquid, followed by stirring for 10minutes. Thus, a slurry was prepared. An opening cock 115 located at alower portion of the dispersion vessel container was opened, and thenwhile compressed air was introduced into the slurry container to keepthe slurry flow rate constant, the slurry was poured to a mesh conveyor121 having a papermaking surface with a width of 200 mm. The slurry wasdrawn with the mesh conveyor 121 at a rate of 1 m/min under suction ofwater, so that a carbon fiber base material 120 having a length of 5 mand a width of 200 mm was obtained (step (I)). Subsequently, an openingcock 128 of the binder vessel 126 was opened and 200 g of the bindersolution was sprinkled to the upper side of the carbon fiber basematerial 120. After an excess binder solution was aspirated, the carbonfiber base material was made to pass through the dryer 138 of 200° C. in3 minutes, so that a carbon fiber base material W2 was obtained (step(II)). The basis weight of the carbon fiber base material W2 was 20g/m². The carbon fiber base material W2 was sent to a double belt press131 by a conveyor 122 while being held online. A non-woven fabric of B1(resin basis weight: 15 g/m²) was arranged as a matrix resin on bothsides of the carbon fiber base material W1 and then was pressurized at220° C., 5 MPa by the use of a double belt pressing machine 131,preparing a prepreg P2 in which the carbon fiber base material had beenimpregnated with the matrix resin (step (III)). It was then directlywound into a roll form at a winding rate of 1 m/min with a windingmachine 133 (step (IV)). The execution conditions of the respectivesteps and the evaluation results of the resulting prepreg P2 are shownin Table 15.

Example 103 Manufacture of Prepreg P3 by Wet Process

A prepreg P3 was obtained by treating in the same manner as in Example101, except for adjusting the water content of the reinforcing fiberbase material of the step (II) to 20% by mass. The execution conditionsof the respective steps and the evaluation results of the resultingprepreg P3 are shown in Table 15.

Example 104 Manufacture of Prepreg P4 by Wet Process

A prepreg P4 was obtained by treating in the same manner as in Example102, except for failing to perform the pressurization and the heating inthe step (III). The execution conditions of the respective steps and theevaluation results of the resulting prepreg P4 are shown in Table 15.

Example 105 Manufacture of Prepreg P5 by Wet Process

A prepreg P5 was obtained by treating in the same manner as in Example101, except for performing double belt press at 250° C. by using anon-woven fabric of B2 (30 g/m²) as the matrix resin in the step (III).The execution conditions of the respective steps and the evaluationresults of the resulting prepreg P5 are shown in Table 15.

Example 106 Manufacture of Prepreg P6 by Wet Process

A prepreg P6 was obtained by treating in the same manner as in Example101, except for performing double belt press at 300° C. by using anon-woven fabric of B3 (30 g/m²) as the matrix resin in the step (III).The execution conditions of the respective steps and the evaluationresults of the resulting prepreg P6 are shown in Table 16.

Example 107 Manufacture of Prepreg P7 by Wet Process

A prepreg P7 was obtained by treating in the same manner as in Example101, except for performing double belt press at 80° C. by using a filmof B4 (30 g/m²) as the matrix resin in the step (III). The executionconditions of the respective steps and the evaluation results of theresulting prepreg P7 are shown in Table 16.

Example 108 Manufacture of Prepreg P8 by Wet Process

Manufacture of Prepreg P8 by Wet Process

Carbon fiber A3 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber (A3-1) was obtained. A prepreg 8 was obtained bytreating in the same manner as in Example 101, except for using A3-1 asthe chopped carbon fiber of step (I). The execution conditions of therespective steps and the evaluation results of the resulting prepreg P8are shown in Table 16.

Example 109 Manufacture of Prepreg P9 by Wet Process

A prepreg P9 was obtained by treating in the same manner as in Example101, except for using C2 as the binder of the step (II). The executionconditions of the respective steps and the evaluation results of theresulting prepreg P9 are shown in Table 16.

Comparative Example 101 Manufacture of Prepreg P10 by Wet Process

A prepreg P10 was obtained by treating in the same manner as in Example101, except for performing the treatments of the steps (I), (II) and(III) offline. The execution conditions of the respective steps and theevaluation results of the resulting prepreg P10 are shown in Table 16.

TABLE 15 Example 101 Example 102 Example 103 Example 104 Example 105 Rawmaterial Reinforcing fiber Kind A1 A1 A1 A1 A1 Cutting length [mm] 6.46.4 6.4 6.4 6.4 Incorporated amount [% by mass] 49.5 49.5 49.5 49.5 49.5Binder Kind C1 C1 C1 C1 C1 Incorporated amount [% by mass] 1 1 1 1 1Matrix resin Kind B1 B1 B1 B1 B2 Form Non-woven Non-woven Non-wovenNon-woven Non-woven fabric fabric fabric fabric fabric Incorporatedamount [% by mass] 49.5 49.5 49.5 49.5 49.5 Step Step (I) Solidconcentration of slurry [% by 0.05 0.05 0.05 0.05 0.05 conditions mass]Mass per unit area [g/m²] of a 60 60 60 60 60 reinforcing fiber basematerial Water content of a reinforcing fiber 8 8 20 8 8 base [% bymass] Reinforcing fiber/solid concentration 100 100 100 100 100 [% bymass] Step (II) Heating step after imparting binder Yes Yes Yes (timetwice) Yes Yes Step (III) Pressurization step Yes Yes Yes No Yes Heatingstep Yes Yes Yes No Yes Reinforcing fiber length [mm] 5 5 5 6.4 5 Step(IV) Winding step — Yes — Yes — Online step (I)-(II) (I)-(II)- (I)-(II)(I)-(II)- (I)-(II) (III)-(IV) (III)-(IV) Offline step (III) — (III) —(III) Evaluation Total process time [min] 40 30 50 30 40 Reinforcingfiber AA, A, B, C AA AA AA AA AA dispersion state Handeability of A, B AA A B A forming base material Flexural strength Relative value 100 100100 100 150 Coefficient of % 3 3 3 3 3 variation

TABLE 16 Comparative Example 106 Example 107 Example 108 Example 109Example 101 Raw material Reinforcing fiber Kind A1 A1 A3 A1 A1 Cuttinglength [mm] 6.4 6.4 6.4 6.4 6.4 Incorporated amount [% by mass] 49.549.5 49.5 49.5 49.5 Binder Kind C1 C1 C1 C2 C1 Incorporated amount [% bymass] 1 1 1 1 1 Matrix resin Kind B3 B4 B1 B1 B1 Form Non-woven FilmNon-woven Non-woven Non-woven fabric fabric fabric fabric Incorporatedamount [% by mass] 49.5 49.5 49.5 49.5 49.5 Step Step (I) Solidconcentration of slurry [% by mass] 0.05 0.05 0.05 0.05 0.05 conditionsMass per unit area [g/m²] of a reinforcing 60 60 60 60 60 fiber basematerial Water content of a reinforcing fiber base 8 8 8 8 8 [% by mass]Reinforcing fiber/solid concentration [% 100 100 100 100 100 by mass]Step (II) Heating step after imparting binder Yes Yes Yes Yes Yes Step(III) Pressurization step Yes Yes Yes Yes Yes Heating step Yes Yes YesYes Yes Reinforcing fiber length [mm] 5 5 5 5 5 Step (IV) Winding step —— — — — Online step (I)-(II) (I)-(II) (I)-(II) (I)-(II) — Offline step(III) (III) (III) (III) (I)-(II)- (III) Evaluation Total process time[min] 40 40 40 40 70 Reinforcing fiber AA, A, B, C AA AA AA AA Bdispersion state Handeability of A, B A A A A A forming base materialFlexural strength Relative value 140 130 90 100 90 Coefficient of % 3 33 3 10 variation

As is clear from Table 15 and Table 16, a prepreg that was superior indispersion state and could maintain high mechanical properties whenbeing processed into a molded product can be obtained in a short time ineach of Examples 101 to 109. It became clear that it was possible toprevent reinforcing fibers from sedimenting or floccurating intransportation by performing the steps (I) to (II) online (see Examples101 to 109 and Comparative Example 101).

Moreover, a prepreg was obtained successfully in a shorter time byperforming the steps (I) to (III) and the step (IV) that may be providedif necessary (see Examples 101, 102, and 104).

It became clear that the heating step after the impartation of a bindercould be finished in a short time by adjusting the water content of thecarbon fiber base material in the step (II) to 10% by mass or less (seeExamples 101, and 103).

It became clear that a matrix resin penetrates a reinforcing fiber basematerial efficiently and the mechanical properties of a prepreg to beobtained could be maintained higher by performing the pressurization andthe heating in the step (III) (see Examples 102, and 103).

If the pressurization and the heating in the step (II) are notperformed, the handleability of a prepreg deteriorates a little but aprocess time can be shortened greatly because a matrix resin fails topenetrate a matrix resin a reinforcing fiber base material.

Example 104

It was also found that the above-mentioned effects are obtained equallyregardless of the kinds of a reinforcing fiber, a matrix resin and abinder (see Examples 101, 105 to 109).

Example 110 Manufacture of Prepreg P11 by Dry Process

A prepreg P5 was produced by using a manufacture apparatus 103 of FIG.11. The manufacture apparatus 103 was composed of a binder vessel 126and a dispersion papermaking vessel 134. The dispersion papermakingvessel 134 is a container of 400 mm in length, 400 mm in width, and 400mm in height and is equipped with a pressurized air tube 29 throughwhich the air can be aspirated and a papermaking surface 119 in thebottom portion. The papermaking surface 119 is a mesh sheet of a size of400 mm in length and 400 mm in width, and a carbon fiber base material120 is to be obtained on this papermaking surface 119. The binder vessel126 has a binder transport portion 127 with an opening cock 128. Theopening of the binder transport portion 127 is located above thedispersion papermaking vessel 112. Moreover, the binder transportportion 127 is movable and can sprinkle a binder uniformly on a carbonfiber base material 120 in the dispersion papermaking vessel 134.

Carbon fiber A2 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber (A2-1) was obtained. A 1%-by-mass aqueousdispersion liquid of C1 had been produced as a binder solution and putinto a binder vessel 126. Into the dispersion papermaking vessel 134were charged 9.6 g of chopped carbon fibers (A2-1), which were opened byspraying pressurized air. Then, the air was aspirated through the bottomsurface and thereby the opened fibers were accumulated on the bottomsurface, so that a carbon fiber base material of 400 mm in length and400 mm in width (step (I)). Subsequently, an opening cock 128 of thebinder vessel 126 was opened and 200 g of the binder was sprinkled fromthe upper side of the carbon fiber base material. An excess of thebinder solution was aspirated, yielding a carbon fiber base material towhich a binder solution had been imparted. The carbon fiber basematerial was taken out and was dried at 150° C. for 20 minutes, yieldinga carbon fiber base material W11 (step (II)). The basis weight of thecarbon fiber base material W11 was 60 g/m². A non-woven fabric of B-1(resin basis weight: 30 g/m²) was arranged as a matrix resin on bothsides of the carbon fiber base material and then was pressurized at 220°C., 10 MPa, yielding a prepreg P5 in which the carbon fiber basematerial had been impregnated with the matrix resin (step (III)). Theexecution conditions of the respective steps and the evaluation resultsof the resulting prepreg P11 are shown in Table 17.

Example 111 Manufacture of Prepreg P12 by Dry Process

A prepreg P6 was produced by using an apparatus 104 of FIG. 12. Themanufacture apparatus 104 has a carding machine 139 which is to performdispersion of a reinforcing fiber bundle, a mesh conveyer 121 which hasat the bottom a papermaking surface of 200 mm in width, a binder vessel126 with an opening cock 128 at a lower portion of a container and abinder transport portion 127 which opens above the mesh conveyor 121, adouble belt press 131 that can horizontally introduce a carbon fiberbase material 120 conveyed by the conveyor 122, a dryer 138 for dryingthe carbon fiber base material 120 on the conveyor 122, and a windingroll 133 capable of winding a prepreg to be obtained.

Carbon fiber A2 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber (A2-1) was obtained. A 1%-by-mass aqueousdispersion liquid of C1 had been produced as a binder solution and putinto a binder vessel 126. The carding machine 139 was charged with 6 gof A2-1 (chopped carbon fibers) uniformly over 30 seconds, and a carbonfiber base material of 200 mm in width was hauled while maintaining thecarding speed at 1 m/min. Subsequently, the opening cock 128 of thebinder vessel 126 was opened, and 200 g of a binder was sprayed onto theupper side of the carbon fiber base material running on the conveyorover 30 seconds. An excess of the binder solution was aspirated online,and then the resultant was allowed to pass through a drying oven of 200°C. in 3 minutes, so that a carbon fiber base material W12 was obtained.The basis weight of the carbon fiber base material W12 was 60 g/m².While the carbon fiber base material was held online, a non-woven fabricof B-1 (resin basis weight: 15 g/m²) was arranged as a matrix resin onboth sides of the carbon fiber base material and then was pressurized at220° C., 5 MPa by the use of a double belt press, preparing a prepreg P6in which the carbon fiber base material had been impregnated with thematrix resin. It was wound up as it was into the form of a roll at withwinding machine 133 at a winding rate of 1 m/min. The executionconditions of the respective steps and the evaluation results of theresulting prepreg P12 are shown in Table 17.

Example 112 Manufacture of Prepreg P13 by Dry Process

A prepreg P13 was obtained by treating in the same manner as in Example106, except for failing to perform the pressurization and the heating inthe step (III). The execution conditions of the respective steps and theevaluation results of the resulting prepreg P13 are shown in Table 17.

Comparative Example 102 Manufacture of Prepreg P12 by Dry Process

A prepreg P14 was obtained by treating in the same manner as in Example1, except for performing the treatments of the steps (I), (II) and (III)offline. The execution conditions of the respective steps and theevaluation results of the resulting prepreg P14 are shown in Table 17.

TABLE 17 Comparative Example 110 Example 111 Example 112 Example 102 Rawmaterial Reinforcing fiber Kind A2 A2 A1 A1 Cutting length [mm] 6.4 6.46.4 6.4 Incorporated amount [% by mass] 49.5 49.5 49.5 49.5 Binder KindC1 C1 C1 C1 Incorporated amount [% by mass] 1 1 1 1 Matrix resin Kind B1B1 B1 B1 Form Non-woven Non-woven Non-woven Non-woven fabric fabricfabric fabric Incorporated amount [% by mass] 49.5 49.5 49.5 49.5 StepStep (I) Opening system Air opening Carding Carding Air openingconditions Mass per unit area [g/m²] of a 60 60 60 60 reinforcing fiberbase material Reinforcing fiber/solid 100 100 100 100 concentration [%by mass] Step (II) Heating step after imparting binder Yes Yes Yes YesStep (III) Pressurization step Yes Yes Yes Yes Heating step Yes Yes NoYes Reinforcing fiber length [mm] 5 5 5 5 Step (IV) Winding step — YesNo — Online step (I)-(II) (I)-(II)- (I)-(II)- — (III)-(IV) (III)-(IV)Offline step (III) — — (I)-(II)- (III) Total process time [min] 20 15 1330 Evaluation Reinforcing fiber AA, A, B, C A A A B dispersion stateHandeability of A, B A A A A forming base material Flexural strengthRelative value 100 100 100 90 Coefficient of variation % 5 5 5 10

As is clear from Table 17, a prepreg that was superior in dispersionstate of carbon fibers and could maintain high mechanical propertieswhen being processed into a molded product can be obtained in a shorttime in each of Examples 110 to 112. It became clear that it waspossible to prevent reinforcing fibers from sedimenting or floccuratingin transportation by performing the steps (I) to (II) online (seeExamples 110 to 112 and Comparative Example 2).

Moreover, a prepreg was obtained successfully in a shorter time byperforming the steps (I) to (III) and the step (IV) that may be providedif necessary (see Examples 110 to 112).

It became clear that a matrix resin penetrates a fiber reinforced basematerial efficiently and the mechanical properties of a prepreg to beobtained could be maintained more higher by performing thepressurization and the heating in the step (III) (see Examples 111 and112).

[Evaluation of the Method for Manufacturing Reinforcing Fiber BaseMaterial by Wet Process]

(Raw Materials Used for Examples)

(Carbon Fiber A4) Pan Type Carbon Fiber

An acrylic fiber bundle having a filament denier of 1 d and the numberof filaments of 12,000 was obtained by the dry-wet type spinning processusing a copolymer composed of 99.4 mol % of acrylonitrile (AN) and 0.6mol % of methacrylic acid. The resulting acrylic fiber bundle was heatedin a draw ratio of 1.05 in the air of a temperature of from 240 to 280°C. to convert it to flame-resistant fibers, and then 10% draw wasapplied in a nitrogen atmosphere within a temperature range of from 300to 900° C. at a temperature elevation rate of 200° C./min, followed bycalcination with a temperature elevation up to 1300° C. The carbon fiberbundle was subjected to electrolytic surface treatment of 3 coulombs pergram of the carbon fibers using an aqueous solution containing sulfuricacid as an electrolyte. Furthermore, a sizing agent was imparted by adipping process and then dried in hot air at a temperature of 120° C.,yielding PAN type carbon fibers A4.

Total number of filaments 12,000 Filament diameter 7 μm Mass per unitlength 0.8 g/m Specific gravity 1.8 g/cm³ Tensile strength (Note 5) 4.2GPa Tensile modulus (Note 6) 230 GPa O/C (Note 7) 0.10 Kind of sizingPolyoxyethylene oleyl ether Amount of attached sizing (Note 8) 1.5% bymass

(Carbon Fiber A5) Pan Type Carbon Fiber

An acrylic fiber bundle having a filament denier of 1 d and the numberof filaments of 12,000 was obtained by the dry-wet type spinning processusing a copolymer composed of 99.4 mol % of acrylonitrile (AN) and 0.6mol % of methacrylic acid. The resulting acrylic fiber bundle was heatedin a draw ratio of 1.05 in the air of a temperature of from 240 to 280°C. to convert it to flame-resistant fibers, and then 10% draw wasapplied in a nitrogen atmosphere within a temperature range of from 300to 900° C. at a temperature elevation rate of 200° C./min, followed bycalcination with a temperature elevation up to 1300° C. Furthermore, asizing agent was imparted by a dipping process and then dried in hot airat a temperature of 120° C., yielding PAN type carbon fibers A5.

Total number of filaments 12,000 Filament diameter 7 μm Mass per unitlength 0.8 g/m Specific gravity 1.8 g/cm³ Tensile strength (Note 5) 4.2GPa Tensile modulus (Note 6) 230 GPa O/C (Note 7) 0.05 Kind of sizingPolyoxyethylene oleyl ether Amount of attached sizing (Note 8) 1.5% bymass

(Film F) Acid-Modified Polypropylene Resin Film

An acid-modified polypropylene resin film F of 50 μm was produced bypress molding an acid-modified polypropylene resin “ADMER” (registeredtrademark) QE510 produced by by Mitsui Chemicals, Inc., (specificgravity: 0.91, melting point: 160° C.) at a temperature of 200° C. andpressure of 20 MPa for 1 minute.

Conditions of Measurement of (Note 5) Tensile Strength, and (Note 6)Tensile Modulus

The condition is the same as the foregoing (Note 1) and (Note 2).

(Note 7) Measurement of O/C

The measurement is the same as the foregoing (Note 3).

(Note 8) Conditions of Measurement of the Amount of Attached SizingAgent

The conditions are the same as the foregoing (Note 4).

(25) (i)-(iv) Process Time

The time required from step (i) to step (iv) was measured.

(26) Evaluation of the Dispersion State of Reinforcing Fibers

A web was cut out in a square shape with a size of 50 mm×50 mm from anarbitrary part of the carbon fiber base material produced by papermakingand it was observed with a microscope. Then, a state that ten or morecarbon filament formed a bundle, that is, the number of bundles ofcarbon fibers with insufficient dispersion was measured. Measurement wasconducted 20 times in this procedure and an average was calculated.Then, evaluation was done on the basis of the following criteria.

AA: There is less than one carbon fiber bundle with insufficientdispersion.

A: There are one or more and less than five carbon fiber bundles withinsufficient dispersion.

B: There are five or more and less than ten carbon fiber bundles withinsufficient dispersion.

C: There are ten or more carbon fiber bundles with insufficientdispersion.

(27) Evaluation of the Mechanical Properties of Molded Product

A carbon fiber base material obtained by papermaking was cut into 200mm×200 mm and was dried at 120° C. for one hour. The carbon fiber basematerial after drying and acid-modified polypropylene resin films F werethree-layer laminated so as to form resin film F/carbon fiber basematerial/resin film F. The laminate was press molded at a temperature of200° C. and a pressure of 30 MPa for 5 minutes and then it was cooled to50° C. while maintaining the pressure, so that a carbon fiber-reinforcedresin sheet with a thickness of 0.12 mm was produced. A carbonfiber-reinforced resin molded product with a thickness of 1.0 mm wasprepared by laminating eight sheets of that resin sheet, press moldingthe laminate at a temperature of 200° C. and a pressure of 30 MPa for 5minutes, and cooling it to 50° C. while maintaining the pressure. Byusing the resulting molded product, flexural strength was evaluated atn=10 in accordance with the ISO178 method (1993). An evaluation resultof the flexural strength was expressed in a relative value on an Example1 base material of 100. The variation of the evaluation results wasexpressed in a coefficient of variation (CV value).

(28) Evaluation of the Viscosity of Dispersion Medium

A beaker was filled up with a dispersion medium, sealed hermetically,and then adjusted to 25° C. in a thermostatic bath. A matching No. 1rotor had been adjusted in advance to 25° C. within the thermostaticbath. Then, the viscosity of the dispersion medium was measured at arotor rotation speed of 60 rpm in accordance with the method disclosedin Attachment 1 of JISK7117-1 (1999) by using a B type viscometer(Model: BBL, manufactured by Tokyo Keiki Inc.). The measurement wasconducted five times and the average thereof was adopted as theviscosity.

(29) Evaluation of Slurry Flow Rate of Transport Portion

When a slurry was transported from a dispersion vessel to a papermakingvessel via a transport portion, there was measured a time T (second)taken for transporting 0.01 m³ of the slurry. Using the transportedamount of the slurry (0.01 m³), the time T taken for the transportation,and the cross-sectional area of the inner diameter of the transportportion S (m^(a)), the slurry flow rate of the transport portion wasdetermined from the following formula.

Slurry flow rate (m/s)=0.01/(S×T)  (Formula)

The measurement was conducted five times and the average thereof wasadopted as the slurry flow rate.

[Evaluation of Method a for Manufacturing a Reinforcing Fiber BaseMaterial by Wet Process] Production Example 201

A reinforcing fiber base material was produced by using an apparatus 201for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 22. The manufacture apparatus 201 is composed of adispersion vessel 211, a papermaking vessel 212, and a transport portion213. The dispersion vessel 211 is a container in a cylindrical form of300 mm in diameter and is equipped with a stirrer 216 in the upperopening of the top opening, and a carbon fiber bundle 217 and adispersion liquid (dispersion medium) 218 can be charged through theopening. As the papermaking vessel 212 is used a large-sizedsquare-shaped sheet machine (No. 2553-I (commercial name), manufacturedby Kumagai Riki Kogyo Co., Ltd.). The bottom of the papermaking vessel212 is equipped with a papermaking surface (made of mesh sheet) 219 of400 mm in length and 400 mm in width. A carbon fiber base material 220is obtained on the papermaking surface 219. The transport portion 213 isa level and linear passage that connects the dispersion vessel 211 andthe papermaking vessel 212 and is provided with a liquid transfer pump(diaphragm pump) 225 in the middle of the passage.

Carbon fiber A4 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A4-1 was obtained. Twenty liters of a dispersionliquid with a concentration of 0.1% by mass composed of water and asurfactant (polyoxyethylene lauryl ether (commercial name), produced byNacalai Tesque, Inc.) was prepared and transferred to a dispersionvessel 211. To this dispersion liquid was charged 9.6 g of choppedcarbon fiber A4-1 (step (i)). A slurry was prepared by stirring for 10minutes (step (ii)). Then, the slurry was started to be poured into thepapermaking vessel 212 (supply rate of slurry: 0.001 m³/sec) via thetransport portion 213 by using the diaphragm pump 225 (step (iii)).Subsequently, water was aspirated, yielding a carbon fiber base material220 of 400 mm in length and 400 mm in width (step (iv)). The basisweight of the carbon fiber base material was 60 g/m². The executionconditions of the respective steps and the evaluation results of theresulting carbon fiber base material are shown in Table 18.

Production Example 202

A carbon fiber base material was obtained by treating in the same manneras in Production Example 201, except for increasing the mass content C1of the chopped carbon fiber A1-1 in the slurry to be prepared in thestep (ii) to 1.5% by mass. The basis weight of the carbon fiber basematerial was 60 g/m². The execution conditions of the respective stepsand the evaluation results of the resulting carbon fiber base materialare shown in Table 18.

Production Example 203

A reinforcing fiber base material was produced by using an apparatus 202for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 23. The manufacture apparatus 202 is composed of adispersion vessel 211, a papermaking vessel 212, a transport portion213, and a conveyor 222. The dispersion vessel 211 and the transportportion 213 are the same as those of the manufacture apparatus 201. Thepapermaking vessel 212 has, at its bottom, a mesh conveyor 221 with apapermaking surface 219 having a width of 200 mm. A carbon fiber basematerial 220 is obtained on the papermaking surface 219. The conveyor222 is disposed following a mesh conveyor 221 and conveys thereinforcing fiber base material 220.

Carbon fiber A4 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A4-1 was obtained. A dispersion liquid with aconcentration of 0.1% by mass composed of water and a surfactant(polyoxyethylene lauryl ether (commercial name), produced by NacalaiTesque, Inc.) was prepared. The dispersion liquid and the chopped carbonfiber A4-1 were started to be charged into the dispersion vessel 211.The charging of the dispersion liquid and the chopped carbon fibers werecontinued continuously while adjusting the charging amount so that thecarbon fiber concentration in the slurry in the dispersion vessel mightbe a fixed concentration and the level H1 of the surface of the slurryin the dispersion vessel might be fixed during the production (step(i)). At the same time when the raw materials were started to be chargedinto the container, stirring was started and a slurry was prepared (step(ii)). Then, the slurry poured into the papermaking vessel 212 (supplyrate of slurry: 0.0014 m³/sec) via the transport portion 213 by usingthe diaphragm pump 225 (step (iii)). By aspirating water from the slurryand the resultant was hauled at a rate of 10 m/min, a carbon fiber basematerial 220 of 200 mm in width was obtained continuously (step iv). Thebasis weight of the carbon fiber base material was 20 g/m². Theexecution conditions of the respective steps and the evaluation resultsof the resulting carbon fiber base material are shown in Table 18.

Production Example 204

A reinforcing fiber base material was produced by using an apparatus 203for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 24. The manufacture apparatus 203 is composed of adispersion vessel 211, a papermaking vessel 212, a transport portion213, and a conveyor 222. The papermaking vessel 212 and the conveyor 222are the same as those of the manufacture apparatus 202. The dispersionvessel 211 is in a recessed shape having two openings (a wide opening223 and a narrow opening 224) in its top surface and is equipped with astirrer 216 in the wide opening 223. The transport portion 213 inclinesdownward from the dispersion vessel 211 toward the papermaking vessel212 (inclination angle: 45°), but has no liquid transfer pump 225 in themidway. A connecting part 214 of the transport portion 213 to thedispersion vessel 211 is located at an upper part (near the openings) ofthe dispersion vessel 211, and the liquid transfer from the dispersionvessel 211 to the papermaking vessel 212 is performed in a overflowsystem.

By using the above-mentioned manufacture apparatus 203, chopped carbonfibers A4-1 and a dispersion liquid with a concentration of 0.1% by masscomposed of water and a surfactant (polyoxyethylene lauryl ether(commercial name), produced by Nacalai Tesque, Inc.) were chargedthrough the narrow opening. Then, a carbon fiber base material wasobtained by treating in the same manner as in Example 203. The basisweight of the resulting carbon fiber base material was 20 g m². Theexecution conditions of the respective steps and the evaluation resultsof the resulting carbon fiber base material are shown in Table 18.

Production Example 205

A carbon fiber base material was obtained by treating in the same manneras in Production Example 204 except for changing the ratio W1/W2 of thewidth W1 of the transport portion to the width W2 of the carbon fiberbase material from 0.6 to 0.2. The basis weight of the resulting carbonfiber base material was 20 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 19.

Production Example 206

A carbon fiber base material was obtained by treating as in the samemanner as in Production Example 201 except for changing the kind ofcarbon fiber from A4 to A5. The basis weight of the resulting carbonfiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 19.

Production Example 207

A carbon fiber base material was obtained by treating in the same manneras in Production Example 201, except for adjusting the time taken forthe step (ii) to 5 minutes (adjusting the time of stirring for slurrypreparation to 5 minutes). The basis weight of the carbon fiber basematerial was 60 g/m². The execution conditions of the respective stepsand the evaluation results of the resulting carbon fiber base materialare shown in Table 19.

Comparative Production Example 201

A carbon fiber base material was obtained by treating in the same manneras in Production Example 202, except for increasing the ratio C1/C2 ofthe mass content C1 of the chopped carbon fibers A4-1 in the slurry tobe prepared in the step (ii) to the mass content C2 of the choppedcarbon fibers A4-1 in the slurry at the commencement of the step (iv) to1.8. The execution conditions of the respective steps and the evaluationresults of the resulting carbon fiber base material are shown in Table19.

TABLE 18 Production Production Production Production Example 201 Example202 Example 203 Example 204 Raw material Reinforcing fiber Kind A4 A4 A4A4 (O/C = 0.10) (O/C = 0.10) (O/C = 0.10) (O/C = 0.10) Cutting length[mm] 6.4 6.4 6.4 6.4 Step Step (i) Raw material supplement No No Yes Yesconditions Step (ii) Mass per unit area [g/m²] of a 60 60 20 20reinforcing fiber base material Reinforcing fiber content C1 [% by 0.051.5 0.05 0.05 mass] Position of slurry surface level H1 Varied VariedFixed Fixed Step (iii) Slurry surface level H1-H2 [m] 0 0 0 0.5 Use ofliquid transfer pump Yes Yes Yes No W1/W2 ratio 0.6 0.6 0.6 0.6 C1/C2ratio 1.0 1.0 1.0 1.0 Online step (i)-(ii) (i)-(ii) (i)-(ii)-(iii)-(iv)(i)-(ii)-(iii)-(iv) Offline step (iii), (iv) (iii), (iv) — — Haulingrate [m/min] — — 10 10 (I) to (IV) process time [min] 20 30 5 5Evaluation Reinforcing fiber AA, A, B, C A-AA A AA AA dispersion stateFlexural strength Relative value 100 100 100 100 Coefficient ofvariation % 3 5 3 3

TABLE 19 Production Production Production Comparative Production Example205 Example 206 Example 207 Example 201 Raw material Reinforcing fiberKind A4 A5 A4 A4 (O/C = 0.10) (O/C = 0.05) (O/C = 0.10) (O/C = 0.10)Cutting length [mm] 6.4 6.4 6.4 6.4 Step conditions Step (i) Rawmaterial supplement Yes No No No Step (ii) Mass per unit area [g/m²] ofa 20 60 60 60 reinforcing fiber base material Reinforcing fiber contentC1 [% by 0.05 0.05 0.05 1.5 mass] Position of slurry surface level H1Fixed Varied Varied Varied Step (iii) Slurry surface level H1-H2 [m] 0.50 0 0 A liquid transfer pump was used. No Yes Yes Yes W1/W2 ratio 0.20.6 0.6 0.6 C1/C2 ratio 1.0 1.0 1.0 1.8 On-line step (i)-(ii)-(iii)-(iv)(i)-(ii) (i)-(ii) (i)-(ii) Off-line step — (iii), (iv) (iii), (iv)(iii), (iv) Hauling rate [m/min] 10 — — — (I) to (IV) process time [min]5 20 15 25 Evaluation Reinforcing fiber AA, A, B, C A-AA A-AA A-AA Cdispersion state Flexural strength Relative value 100 90 100 90Coefficient of variation % 3 3 3 10

As is clear from Table 18 and Table 19, a carbon fiber base materialwith good dispersion state was obtained successfully in each ofProduction Examples 201 through 207. Specifically, by adjusting theC1/C2 ratio to within the range of from 0.8 to 1.2, it becameunnecessary to perform excess steps such as concentration dilution inthe respective steps and carbon fiber base materials superior indispersion state were obtained successfully (see Production Examples 201to 207, and Comparative Production Example 201). Moreover, the carbonfiber base materials obtained in Production Examples 201 to 207 werefound to be superior in mechanical properties of molded product whenbeing processed into molded products.

By adjusting the concentration C1 to a relatively low concentration, itbecomes possible to perform treatment in a short time (see ProductionExamples 201 and 202). Moreover, by performing the steps (i) to (iv)online, or moreover by using an overflow system without using any pumpin a transport portion, it was possible to perform treatment in ashorter time (see Production Examples 201, 203 to 205).

Through the adjustment of W1/W2 ratio to from 0.5 to 1.0, the dispersionstate of a carbon was improved successfully (see Production Examples 204and 205).

It has become clear that the mechanical properties of a molded productof a carbon fiber base material can be improved by the use of fiberswith high O/C (see Production Examples 201 and 206).

[Evaluation of Method b for Manufacturing Reinforcing Fiber BaseMaterial by Wet Process] Production Example 301

A reinforcing fiber base material was produced by using an apparatus 301for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 25. The manufacture apparatus 301 is composed of adispersion vessel 311, a papermaking vessel 212, and a transport portion313. The dispersion vessel 311 is a container in a cylindrical form of300 mm in diameter and is equipped with an opening cock 315 at a lowerpart of the container and a stirrer 316 in the upper opening. Throughthe opening can be charged a carbon fiber bundle 317 and a dispersionliquid (dispersion medium) 318. As the papermaking vessel 312 is used alarge-sized square-shaped sheet machine (No. 2553-I (commercial name),manufactured by Kumagai Riki Kogyo Co., Ltd.), and it has a papermakingsurface 319 (made of mesh sheet) of 400 mm in length and 400 mm inwidth. A carbon fiber base material 320 is obtained on the papermakingplane 319. The transport portion 313 is a linear passage that connectsthe dispersion vessel 311 and the papermaking vessel 312 and inclinesdownward from the dispersion vessel 311 toward the papermaking vessel312 (inclination angle: 45°). The dispersion vessel 311 and thetransport portion 313 are connected via the opening cock 315.

Carbon fiber A4 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A4-1 was obtained. Twenty liters of a dispersionliquid composed of water and a surfactant (polyoxyethylene lauryl ether(commercial name), produced by Nacalai Tesque, Inc.) with aconcentration of 0.1% by mass was prepared and transferred to adispersion vessel 311. To this dispersion liquid was charged 9.6 g ofchopped carbon fiber A4-1 (step (i)). A slurry was prepared by stirringfor 10 minutes (step (ii)). Then, the opening cock 315 located at thelower portion of the container was opened and thereby the slurry waspoured into the papermaking vessel 312 through the transport portion 313(step (iii)). At this time, the level H1 of the slurry surface in thedispersion vessel was at a position only 50 cm higher than the slurrysurface H2 in the papermaking vessel. Subsequently, water was aspiratedthrough the papermaking surface 319 of the papermaking vessel, yieldinga carbon fiber base material 320 of 400 mm in length and 400 mm in width(step (iv)). The basis weight of the carbon fiber base material was 60g/m². The execution conditions of the respective steps and theevaluation results of the resulting carbon fiber base material are shownin Table 20.

Production Example 302

A reinforcing fiber base material was produced by using an apparatus 302for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 26. The manufacture apparatus 302 is composed of adispersion vessel 311, a papermaking vessel 312, a transport portion313, and a conveyor 322. The dispersion vessel 311 and the transportportion 313 are the same as those of the manufacture apparatus 301. Thepapermaking vessel 312 has, at its bottom, a mesh with a papermakingplane 319 having a width of 200 mm. A carbon fiber base material 320 isobtained on the papermaking plane 319. The conveyor 322 is disposedfollowing a mesh conveyor 321 and conveys the reinforcing fiber basematerial 320.

Carbon fiber A4 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A4-1 was obtained. A dispersion liquid composed ofwater and a surfactant (polyoxyethylene lauryl ether (commercial name),produced by Nacalai Tesque, Inc.) with a concentration of 0.1% by masswas prepared. The dispersion liquid and the chopped carbon fiber A4-1were started to be charged into the dispersion vessel 311. The chargingof the dispersion liquid and the chopped carbon fibers were continuedcontinuously while adjusting the charging amount so that the carbonfiber concentration in the slurry in the dispersion vessel might be afixed concentration and the level H1 of the surface of the slurry in thedispersion vessel might be fixed during the production (step (i)). Atthe same time when the raw materials were started to be charged into thecontainer, stirring was started and a slurry was prepared (step (ii)).When 40 liters of slurry was accumulated, the opening cock 315 of thelower part of the container was opened, so that the slurry was pouredinto the papermaking vessel 312 via the transport portion 313 (step(iii)). At this time, the level H1 of the slurry surface in thedispersion vessel was at a position only 50 cm higher than the slurrysurface H2 in the papermaking vessel. By aspirating water from theslurry and the resultant was hauled at a rate of 10 m/min, a carbonfiber base material 320 of 200 mm in width was obtained continuously(step iv). The basis weight of the carbon fiber base material was 20g/m². The execution conditions of the respective steps and theevaluation results of the resulting carbon fiber base material are shownin Table 20.

Production Example 303

A reinforcing fiber base material was produced by using an apparatus 303for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 27. The manufacture apparatus 303 is composed of adispersion vessel 311, a papermaking vessel 312, a transport portion313, and a conveyor 322. The papermaking vessel 312, the transportportion 313, and the conveyor 322 are the same as those of themanufacture apparatus 302. The dispersion vessel 311 is in a recessedshape having two openings (a wide opening 323 and a narrow opening 324)in its top surface and is equipped with a stirrer 316 in the wideopening 323. A connecting part 314 of the transport portion 313 to thedispersion vessel 311 is located at an upper part (near the openings) ofthe dispersion vessel 311, and the liquid transfer from the dispersionvessel 311 to the papermaking vessel 312 is performed in a overflowsystem. The connecting portion 314 is provided with no opening cock.

By using the above-mentioned manufacture apparatus 303, chopped carbonfibers A4-1 and a dispersion liquid with a concentration of 0.1% by masscomposed of water and a surfactant (polyoxyethylene lauryl ether(commercial name), produced by Nacalai Tesque, Inc.) were chargedthrough the narrow opening 324. Then, a carbon fiber base material wasobtained by treating in the same manner as in Production Example 302.The basis weight of the resulting carbon fiber base material was 20g/m². The execution conditions of the respective steps and theevaluation results of the resulting carbon fiber base material are shownin Table 20.

Production Example 304

A reinforcing fiber base material was produced by using an apparatus 304for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 27. The manufacture apparatus 304 is composed of adispersion vessel 311, a papermaking vessel 312, a transport portion313, and a conveyor 322. The dispersion vessel 311, the papermakingvessel 312, and the conveyor 322 are the same as those of themanufacture apparatus 303. The transport portion 313 is of a structurein which the portion is bent at right angle at four point and has anangle of 45° as a whole.

A carbon fiber base material was obtained in the same manner as inProduction Example 303 by the use of the manufacture apparatus 304described above. The basis weight of the resulting carbon fiber basematerial was 20 g/m². The execution conditions of the respective stepsand the evaluation results of the resulting carbon fiber base materialare shown in Table 20.

Production Example 305

A manufacture apparatus (not shown) that was the same as the manufactureapparatus 303 except for having a structure in which the angel of thetransport portion was 90° (perpendicularly downward). A carbon fiberbase material was obtained by treating in the same manner as inProduction Example 303. The basis weight of the resulting carbon fiberbase material was 20 g/m². The execution conditions of the respectivesteps and the evaluation results of the resulting carbon fiber basematerial are shown in Table 20.

Production Example 306

A manufacture apparatus 303 was used. A carbon fiber base material wasobtained by treating in the same manner as in Production Example 305except for changing the ratio W1/W2 of the width W1 of the transportportion to the carbon fiber base material W2 from 0.6 to 0.2. The basisweight of the resulting carbon fiber base material was 20 g/m². Theexecution conditions of the respective steps and the evaluation resultsof the resulting carbon fiber base material are shown in Table 21.

Production Example 307

A carbon fiber base material was obtained by treating as in the samemanner as in Production Example 301 except for changing the kind ofcarbon fiber from A4 to A5. The basis weight of the resulting carbonfiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 21.

Comparative Production Example 301

A manufacture apparatus 301 was used. A carbon fiber base material wasobtained by treating in the same manner as in Production Example 301,except for performing only the steps (i) to (ii) online and performingthe steps (iii) to (iv) offline. The basis weight of the resultingcarbon fiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 21.

Comparative Production Example 302

There was used a manufacture apparatus (not shown) which was the same asthe manufacture apparatus 301 except that the transport portion was in ahorizontal straight form (angle: 0°) and equipped with a liquid transferpump. A carbon fiber base material was obtained by treating in the samemanner as in Production Example 301. The basis weight of the resultingcarbon fiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 21.

TABLE 20 Production Production Production Production Production Example301 Example 302 Example 303 Example 304 Example 305 Raw Reinforcingfiber Kind A4 A4 A4 A4 A4 material (O/C = 0.10) (O/C = 0.10) (O/C =0.10) (O/C = 0.10) (O/C = 0.10) Cutting length [mm] 6.4 6.4 6.4 6.4 6.4Step Step (i) Solid concentration of a slurry 0.05 0.05 0.05 0.05 0.05conditions [% by mass] Raw material supplement No Yes Yes Yes Yes Step(ii) Mass per unit area [g/m²] of a 60 20 20 20 20 reinforcing fiberbase material Position of slurry surface Varied Fixed Fixed Fixed Fixedlevel H1 Step (iii) Slurry surface level H1-H2 0.5 0.5 0.5 0.5 0.5 [m]Use of liquid transfer pump No No No No No Shape of a transport portionStraight Straight Straight Bent at riight Straight angle Inclinationangle of transport 45 45 45 45 90 portion [°] W1/W2 ratio 0.6 0.6 0.60.6 0.6 Online step (i)-(ii)-(iii)-(iv) (i)-(ii)-(iii)-(iv)(i)-(ii)-(iii)-(iv) (i)-(ii)-(iii)-(iv)-(v) (i)-(ii)-(iii)-(iv) Offlinestep — — — — — Hauling rate [m/min] — 10 10 10 10 Evaluation (I) to (IV)[min] 15 5 5 5 5 process time Reinforcing fiber AA, A, B, C AA AA AA A Adispersion state Flexural strength Relative value 100 100 100 100 100Coefficient of % 3 3 3 5 5 variation

TABLE 21 Comparative Production Production Comparative ProductionProduction Example 306 Example 307 Example 301 Example 302 RawReinforcing fiber Kind A4 A5 A4 A4 material (O/C = 0.10) (O/C = 0.05)(O/C = 0.10) (O/C = 0.10) Cutting length [mm] 6.4 6.4 6.4 6.4 Step Step(i) Solid concentration of a slurry [% 0.05 0.05 0.05 0.05 conditions bymass] Raw material supplement Yes No No No Step (ii) Mass per unit area[g/m²] of a 20 60 60 60 reinforcing fiber base material Position ofslurry surface level H1 Fixed Varied Varied Varied Step (iii) Slurrysurface level H1-H2 [m] 0.5 0.5 0.5 0 Use of liquid transfer pump No NoNo Yes Shape of a transport portion Straight Straight Straight StraightInclination angle of a transport 45 45 45 0 portion [°] W1/W2 ratio 0.20.6 0.6 0.6 Online step (i)-(ii)-(iii)-(iv) (i)-(ii)-(iii)-(iv) (i)-(ii)(i)-(ii)-(iii)-(iv) Offline step — — (iii), (iv) — Hauling rate [m/min]10 — — 10 Evaluation (I) to (IV) process time [min] 5 15 25 15Reinforcing fiber AA, A, B, C A AA B C dispersion state Flexuralstrength Relative value 100 90 90 70 Coefficient of variation % 5 3 1015

As is clear from Table 20 and Table 21, a carbon fiber base materialwith good dispersion state without reflocculation was obtainedsuccessfully in a short time in each of Production Examples 301 through307. It became clear that by performing the steps (i) to (iv) online andtransferring a liquid without using a liquid transfer pump, it waspossible to prevent reinforcing fibers from sedimentation andreflocculation in transportation (see Production Examples 1 to 7 andComparative Production Examples 1 to 2). Moreover, the carbon fiber basematerials obtained in Production Examples 301 to 307 were found to besuperior in mechanical properties of molded product when being processedinto molded products.

By adjusting the level H1 of the surface of a slurry to be constantwhile charging a dispersion liquid and chopped carbon fiberscontinuously into a dispersion vessel or by further configuring atransport portion to be of an overflow system, it was possible toperform treatment in a shorter time (see Production Examples 302 to306).

By making a transport portion to have a straight form and adjusting aninclination angle to from 30 to 60° or adjusting a W1/W2 ratio to from0.5 to 1.0, the dispersion state of a carbon fiber base material wasimproved successfully (see Production Examples 301 to 304, and 307).

It has become clear that the mechanical properties of a molded productof a carbon fiber base material can be improved by the use of fiberswith high O/C (see Production Examples 301 and 307).

[Evaluation of Method c for Manufacturing Reinforcing Fiber BaseMaterial by Wet Process] Production Example 401

A reinforcing fiber base material was produced by using an apparatus 401for manufacturing a reinforcing fiber base material (papermaking basematerial) of FIG. 29. The manufacture apparatus 401 is composed of adispersion vessel 411, a papermaking vessel 412, and a transport portion413. The dispersion vessel 411 is a container in a cylindrical form of300 mm in diameter and is equipped with an opening cock 415 at a lowerpart of the container and a stirrer 416 in the upper opening. Throughthe opening can be charged a carbon fiber bundle 417 and a dispersionliquid (dispersion medium) 418. As the papermaking vessel 412 is used isused a large-sized square-shaped sheet machine (No. 2553-I (commercialname), manufactured by Kumagai Riki Kogyo Co., Ltd.), and it has apapermaking surface 419 (made of mesh sheet) of 400 mm in length and 400mm in width. A carbon fiber base material 420 is obtained on thepapermaking plane 419. The transport portion 413 is a linear passagethat connects the dispersion vessel 411 and the papermaking vessel 412and inclines downward from the dispersion vessel 411 toward thepapermaking vessel 412 (inclination angle r: 88°). The cross-sectionalshape of the transport portion 413 is a circle of 0.01 m in diameter.

Carbon fiber A1 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A4-1 was obtained. Twenty liters of a dispersionliquid with a concentration of 0.25% by mass composed of water and awater-soluble polymer (PEO-8Z (commercial name), produced by SumitomoSeika Chemicals Co., Ltd.) was prepared and transferred to thedispersion vessel 411. The dispersion liquid had a viscosity of 10mPa·s. To this dispersion liquid was charged 9.6 g of chopped carbonfiber A4-1 (step (i)). A slurry was prepared by stirring for 10 minutes(step (ii)). Then, the opening cock 415 located at the lower portion ofthe container was opened and thereby the slurry was poured into thepapermaking vessel 412 through the transport portion 413 (step (iii)).Subsequently, water was aspirated through the papermaking surface 419 ofthe papermaking vessel, yielding a carbon fiber base material 420 of 400mm in length and 400 mm in width (step (iv)). The basis weight of thecarbon fiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 22.

Production Example 402

A manufacture apparatus (not shown) was used which was the same as themanufacture apparatus 401 except that the inclination angle r was 65°. Acarbon fiber base material was obtained by treating in the same manneras in Production Example 401. The basis weight of the resulting carbonfiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 22.

Production Example 403

A carbon fiber base material was obtained by treating in the same manneras in Production Example 401, except for preparing 20 L of a dispersionof a concentration of 0.1% by mass composed of water a water-solublepolymer (PEO-8Z (commercial name), produced by Sumitomo Seika ChemicalsCo., Ltd.). The basis weight of the resulting carbon fiber base materialwas 60 g/m². The execution conditions of the respective steps and theevaluation results of the resulting carbon fiber base material are shownin Table 22.

Production Example 404

A carbon fiber base material was obtained by performing treatment in thesame manner as in Production Example 401, except for preparing 20 L of adispersion having a concentration of 1% by mass composed of water awater-soluble polymer (PEO-8Z (commercial name), produced by SumitomoSeika Chemicals Co., Ltd.). The basis weight of the resulting carbonfiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 22.

Production Example 405

A manufacture apparatus (not shown) was used which was the same as themanufacture apparatus 401 except that the sectional shape of itstransport portion 13 was a square 0.01 m long on each side. A carbonfiber base material was obtained by treating in the same manner as inProduction Example 401. The basis weight of the resulting carbon fiberbase material was 60 g/m². The execution conditions of the respectivesteps and the evaluation results of the resulting carbon fiber basematerial are shown in Table 23.

Production Example 406

A carbon fiber base material was obtained by treating in the same manneras in Production Example 401 except for cutting carbon fiber A5 into 6.4mm with a cartridge cutter to obtain chopped carbon fiber A5-1 andcharging 9.6 g of the chopped carbon fiber A5-1 to a dispersion liquidin the step (i). The basis weight of the resulting carbon fiber basematerial was 60 g/m². The execution conditions of the respective stepsand the evaluation results of the resulting carbon fiber base materialare shown in Table 23.

Comparative Production Example 401

A manufacture apparatus (not shown) was used which was the same as themanufacture apparatus 401 except that the inclination angle r was 0°. Acarbon fiber base material was obtained by treating in the same manneras in Production Example 401. The basis weight of the resulting carbonfiber base material was 60 g/m². The execution conditions of therespective steps and the evaluation results of the resulting carbonfiber base material are shown in Table 23.

Comparative Production Example 402

A manufacture apparatus (not shown) was used which was the same as themanufacture apparatus 401 except for having a liquid transfer pump inits transport portion. A carbon fiber base material was obtained bytreating in the same manner as in Production Example 401. The basisweight of the resulting carbon fiber base material was 60 g/m². Theexecution conditions of the respective steps and the evaluation resultsof the resulting carbon fiber base material are shown in Table 23.

TABLE 22 Production Production Production Example 401 Example 402Production Example 403 Example 404 Raw Reinforcing fiber Kind A4 A4 A4A4 material (O/C = 0.10) (O/C = 0.10) (O/C = 0.10) (O/C = 0.10) Cuttinglength [mm] 6.4 6.4 6.4 6.4 Step Step (i) Solid concentration of aslurry 0.05 0.05 0.05 0.05 conditions [% by mass] Step (ii) Mass perunit area [g/m²] of a 60 60 60 60 reinforcing fiber base materialViscosity of dispersion medium 10 10 5 120 [mPa · s] Step (iii) Use ofliquid transfer pump No No No No Shape of a transport portion CircleCircle Circle Circle Representative length of a 0.01 0.01 0.01 0.01transport portion [m] State of flow Laminar flow Transition region fromTransition region from Laminar flow laminar flow to turbulent laminarflow to turbulent flow flow Flow rate [m/s] 1 4 2 0.5 Reynolds number1000 4000 4000 40 Evaluation Reinforcing fiber AA, A, B, C AA A AA AAdispersion state Flexural strength Relative value 100 100 100 85Coefficient of % 3 5 3 3 variation

TABLE 23 Comparative Comparative Production Production ProductionProduction Example 405 Example 406 Example 401 Example 402 Raw materialReinforcing fiber Kind A4 A5 A4 A4 (O/C = 0.10) (O/C = 0.05) (O/C =0.10) (O/C = 0.10) Cutting length [mm] 6.4 6.4 6.4 6.4 Step conditionsStep (i) Solid concentration of a slurry 0.05 0.05 0.05 0.05 [% by mass]Step (ii) Mass per unit area [g/m²] of a 60 60 20 60 reinforcing fiberbase material Viscosity of dispersion medium 10 10 10 10 [mPa · s] Step(iii) Use of liquid transfer pump No No No Yes Shape of a transportportion Square Circle Circle Circle Representative length of a 0.01 0.010.01 0.01 transport portion [m] State of flow Laminar flow Laminar flowturbulent flow turbulent flow Flow rate [m/s] 2 1 12 4 Reynolds number2000 1000 12000 200000 Evaluation Reinforcing fiber AA, A, B, C AA AA BC dispersion state Flexural strength Relative value 100 80 95 90Coefficient of % 3 3 10 15 variation

As is clear from Table 22 and Table 23, the reinforcing fiber did notreflocculate and a carbon fiber base material with good dispersion statewas obtained successfully in each of Production Examples 401 through406. It became clear that it was possible to prevent reinforcing fibersfrom reflocculating in transportation by transporting a slurry in atransport portion in a laminar flow state or in a state of a transitionregion from a laminar flow to a turbulent flow (see Production Examples401 to 406 and Comparative Production Examples 401 to 402).

It became clear that it was possible to prevent reinforcing fibers fromreflocculating in transportation by transporting a slurry in a transportportion in a laminar flow state or in a state of a transition regionfrom a laminar flow to a turbulent flow even if the cross-sectionalshape of the transport portion is either a circle or a quadrangle (apolygon) (see Production Examples 401 and 405).

It is expected that it is possible to increase the mechanical propertiesof carbon fiber base materials or molded products by adjusting theviscosity of a dispersion medium to from 1 to 100 mPa·s. (See ProductionExamples 402, 403, and 404.)

It is expected that it is possible to increase the mechanical propertiesof carbon fiber base materials or their molded products by using fiberswith a high O/C.

[Evaluation (2) of Prepreg, Preform, and Molded Product]

The evaluation and the measurement of various properties were carriedout in the same methods as those described in “Evaluation (1) ofprepreg, preform, and molded product.”

Example 501

A prepreg was produced by using an apparatus 102 of FIG. 10.

Carbon fiber A1 was cut into 6.4 mm with a cartridge cutter, so thatchopped carbon fiber A1 was obtained. A 1%-by-mass aqueous dispersionliquid (emulsion) of C1 had been produced as a binder solution and putinto a binder vessel 126. Forty liters of a dispersion liquid composedof water and a surfactant (polyoxyethylene lauryl ether (commercialname), produced by Nacalai Tesque, Inc.) with a concentration of 0.1% bymass was prepared and transferred to a dispersion vessel 111. Fiftygrams of chopped carbon fiber was added to this dispersion liquid,followed by stirring for 10 minutes. Thus, a slurry was prepared. Anopening cock 115 located at a lower portion of the dispersion layercontainer was opened, and then while compressed air was introduced intothe slurry container to keep the slurry flow rate constant, the slurrywas poured to a mesh conveyor having a papermaking plane with a width of200 mm. The slurry was drawn with the mesh conveyor at a rate of 1 m/minunder aspiration of water, so that a carbon fiber base material 120having a length of 5 m and a width of 200 mm was obtained (step (I)).Subsequently, an opening cock 128 of the binder vessel 126 was openedand 200 g of the binder solution was sprinkled to the upper side of thecarbon fiber base material 120. After an excess binder solution wasaspirated, the carbon fiber base material was made to pass through thedryer 138 of 200° C. for three minutes, so that a carbon fiber basematerial W2 was obtained (step (II)). The basis weight of the carbonfiber base material W2 was 50 g/m². The carbon fiber base material W2was sent to a double belt pressing machine 131 by a conveyor while beingheld online. It was laminated with two films of CM1007 (Nylon 6 resin)produced by Toray Industries, Inc., as a matrix resin which were equalin thickness so as to form film/carbon fiber base material/film,followed by application of pressure at a temperature of 250° C. and apressure of 5 MPa for two minutes by the use of the double belt pressingmachine 131. Thus, a prepreg (28) in which the carbon fiber basematerial had been impregnated with the matrix resin was produced (step(III)). It was then directly wound into a roll form at a winding rate of1 m/min with a winding machine 133 (step (IV)). The properties of theprepreg are shown in Table 25.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which eight prepregs(28) had been laminated. The preform was shaped well in conformity withthe shape of the mold and a molded product that was high in shapequality was obtained. The properties of the molded product are shown inTable 26.

Example 502

A prepreg was produced by using the apparatus 202 of FIG. 23 as thepapermaking apparatus disposed upstream from the dryer 138 in theapparatus 102 of FIG. 10. By using the manufacture apparatus, adispersion liquid with a concentration of 0.1% by mass composed of waterand a surfactant (polyoxyethylene lauryl ether (commercial name)produced by Nacalai Tesque, Inc.), and chopped carbon fibers usingcarbon fibers A1 were charged through the narrow opening. Then, aprepreg (29) was obtained by treating in the same manner as in Example501. The carbon fiber content in the slurry was 0.05% by mass and thecarbon fiber concentration difference of the slurry, C1/C2, was 1.0. Theproperties of the resulting prepreg are shown in Table 25.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which eight prepregs(29) had been laminated. The preform was shaped well in conformity withthe shape of the mold and a molded product that was high in shapequality was obtained. The properties of the molded product are shown inTable 26.

Example 503)

A prepreg was produced by using the apparatus 303 of FIG. 27 as thepapermaking apparatus disposed upstream from the dryer 138 in theapparatus 102 of FIG. 10. By using the manufacture apparatus, adispersion liquid with a concentration of 0.1% by mass composed of waterand a surfactant (polyoxyethylene lauryl ether (commercial name)produced by Nacalai Tesque, Inc.), and chopped carbon fibers usingcarbon fibers A1 were charged through the narrow opening. Then, aprepreg (30) was obtained by treating in the same manner as in Example501. The level of the surface of the slurry, H1−H2, was 0.5 m, the shapeof the transport portion was straight, and the angle of inclination ofthe transport portion was 45°. The properties of the resulting prepregare shown in Table 25.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which eight prepregs(30) had been laminated. The preform was shaped well in conformity withthe shape of the mold and a molded product that was high in shapequality was obtained. The properties of the molded product are shown inTable 26.

Example 504

A prepreg was produced by using the apparatus 303 of FIG. 27 as thepapermaking apparatus disposed upstream from the dryer 138 in theapparatus 102 of FIG. 10. It is noted that the cross-sectional shape ofthe transport portion (inclination angle r: 88°) of the apparatus 303 isa circle of 0.01 m in diameter. By using the manufacture apparatus, adispersion liquid with a concentration of 0.25% by mass composed ofwater and a water-soluble macromolecule (PEO-8Z (commercial name)produced by Sumitomo Seika Chemicals Co., Ltd.), and chopped carbonfibers using carbon fibers A1 were charged through the narrow opening.Then, a prepreg (31) was obtained by treating in the same manner as inExample 501. The viscosity of the dispersion medium was 10 mPa·s. Thestate of flow in the transport portion was laminar flow, whose flow ratewas 1 m/s and Reynolds number was 1000. The properties of the resultingprepreg are shown in Table 25.

An L-shaped box-like molded product was produced in the same manner asin Example 1 except for manufacturing a preform in which eight prepregs(31) had been laminated. The preform was shaped well in conformity withthe shape of the mold and a molded product that was high in shapequality was obtained. The properties of the molded product are shown inTable 26.

TABLE 24 Example 501 Example 502 Example 503 Example 504 ReinforcingReinforcing Kind of fiber [—] Carbon Carbon Carbon Carbon fiber basefiber fiber A1 fiber 1 fiber 1 fiber 1 material Fiber mass content [% bymass] 28 27 28 28 Fiber length Longer than 10 mm [% by mass] 0 0 0 0Proportion 2 to 10 mm [% by mass] 95 95 95 95 Shorter than 2 mm [% bymass] 5 5 5 5 Two-dimensional orientation angle [°] 40 41 41 41 Amountof air (Frazier method) [cm³/cm² · s] 160 160 160 160

TABLE 25 Example 501 Example 502 Example 503 Example 504 Prepreg Prepregnumber [—]  (28)  (29)  (30)  (31) Resin Kind of resin [—] Nylon 6 Nylon6 Nylon 6 Nylon 6 Resin mass content [% by mass]  72  72  72  72 FeatureThickness at 23° C., hp0 [mm]    0.15    0.15    0.15    0.15 Thicknessat 100° C., h1 [mm]    0.15    0.15    0.15    0.15 Thickness at 200°C., h2 [mm]    0.18    0.18    0.18    0.18 Thickness at 300° C., h3[mm]    0.92    0.92    0.92    0.92 (*2) (*2) (*2) (*2) Thickness at400° C., h4 [mm] (*1) (*1) (*1) (*1) Resin impregnation ratio [%]  95 95  95  95 Bulk density [g/cm³]    1.20    1.20    1.20    1.20 Massper unit area [g/m²] 180 180 180 180 Tensile strength σ [MPa] 150 150150 150 σMax [MPa] 170 170 170 170 σMim [MPa] 140 140 140 140 Length inthe longitudinal direction [mm] 5000  5000  5000  5000  (*1): Resin wasdecomposed. (*2): Resin was slightly decomposed.

TABLE 26 Example 501 Example 502 Example 503 Example 504 Molded Moldingmethod Stamping Heat press Stamping Stamping product Properties Specificstrength B B B B Isotropy A A A A Specific rigidity B B B B Isotropy A AA A Coefficient of linear expansion A A A A Isotropy A A A A

The prepregs produced in Examples 501 to 504 were good in distributionof the fiber length of reinforcing fibers, thickness and tensilestrength, and were isotropic within a range of two-dimensionalorientation angle of from 10 to 80°, and molded products producetherefrom exhibited good properties. In addition, laminated preformsproduced using these prepregs also demonstrated good properties.Moreover, a continuous prepreg can be obtained in the form of a roll andtherefore it is advantageous in industrial execution.

INDUSTRIAL APPLICABILITY

The prepreg the present invention and a laminated article thereof can besuitably used as a fiber-reinforced preform that can reconcilemechanical properties and moldability simultaneously; in particular,since reinforcing fibers constituting a thin prepreg have been orientedwith two-dimensional isotropy, the prepreg is superior in reinforcingeffect in its plane direction and inhibits interference of reinforcingfibers in the intralayer thickness direction, and since there is lessinterlayer interaction, it is superior in shapability in molding. Thesecan be applied to a wide variety of industrial fields, such ascomponents, parts and housings of electric and electronic instruments,robots, motorcycles, cars, and airplanes.

EXPLANATION OF REFERENTIAL SIGNS

-   -   1 Reinforcing filament (a)    -   2 to 7 Reinforcing filament (b)    -   8 Two-dimensional orientation angle    -   9 Stainless steel mesh    -   10 Prepreg    -   11 Reinforcing fiber base material    -   12 Fiber direction    -   13 Fiber orthogonal direction    -   14 Carbon fiber prepreg with cut    -   15 Carbon fiber    -   16 Cut    -   17 Cut length    -   18 Fiber length    -   19 Length with which cuts of adjacent lines overlap with each        other    -   21 Dispersion vessel    -   22 Papermaking vessel    -   25 Opening cock    -   26 Stirrer    -   27 Chopped reinforcing fiber    -   28 Dispersion liquid (dispersion medium)    -   30 Reinforcing fiber base material (papermaking base material)    -   31 Mesh conveyor    -   32 Conveyor    -   41 Continuous CFRP    -   42 Prepreg    -   43 GMT    -   t Prepreg thickness direction    -   R Radius of curvature    -   101,102,103,104 Apparatus    -   111 Dispersion vessel    -   112 Papermaking vessel    -   113 Transport portion    -   115,128 Opening cock    -   116 Stirrer    -   117 Chopped carbon fiber (carbon fiber bundle)    -   118 Dispersion liquid (dispersion medium)    -   119 Papermaking side    -   120 Reinforcing fiber base material (Papermaking base material)    -   121 Mesh conveyor    -   122 Conveyor    -   126 Binder vessel    -   127 Binder transport portion    -   129,130 Pressurized air pipe    -   131 Double belt press    -   132 Prepreg    -   133 Winding machine    -   134 Dispersion-papermaking vessel    -   135 Matrix resin    -   136, 137 Roll    -   138 Dryer    -   139 Carding machine    -   PA Pressurized air    -   201-203, 301-304, 401 Apparatus for manufacturing a reinforcing        fiber base material (papermaking base material)    -   211, 311, 411 Dispersion vessel    -   212, 312, 412 Papermaking vessel    -   213, 313, 413 Transport portion    -   214, 314, 414 Connecting portion between transport portion and        dispersion vessel    -   315, 415 Opening cock    -   216, 316, 416 Stirrer    -   217, 317, 417 Chopped carbon fiber (carbon fiber bundle)    -   218, 318, 418 Dispersion liquid (dispersion medium)    -   219, 319, 419 Papermaking surface (mesh sheet)    -   220, 320, 420 Reinforcing fiber base material (papermaking base        material)    -   221, 321 Mesh conveyor    -   222, 322 Conveyor    -   223, 323 Wide opening    -   224, 324 Narrow opening    -   225 Liquid transfer pump (low shear pump, diaphragm pump)    -   H1 Level of the surface of slurry in step (ii)    -   H2 Level of the surface of slurry in step (iv)    -   A Standard    -   B The surface of slurry in step (ii)    -   C The surface of slurry in step (iv)    -   p Line that is parallel to the gravity direction    -   q Central line of transport division    -   r Angle which p and q form in the perpendicularly lower side    -   C1, C2 Mass content of reinforcing fibers in slurry    -   D Fiber diameter    -   L Fiber length    -   n The number of fibers per unit volume    -   *1 Burning off of resin    -   *2 Aspiration    -   *3 A tip works so that it can perform uniform sprinkle.    -   *4 Heating, pressurization, and cooling    -   *5 Winding    -   *6 Overflow

1. A method for manufacturing a prepreg, the method comprising step (I)of dispersing a reinforcing fiber bundle to obtain a reinforcing fiberbase material, step (II) of providing a binder to the reinforcing fiberbase material produced in the step (I), and step (III) of hybridizing amatrix resin composed of a thermoplastic resin with the reinforcingfiber base material provided with the binder produced in the step (II),wherein the steps (I) to (II) are carried out online and the prepreg isone such that the content of the reinforcing fiber bundle relative tothe whole portion of the prepreg is from 10 to 80% by mass, the contentof the binder relative to the whole portion of the prepreg is from 0.1to 10% by mass, and the content of the matrix resin relative to thewhole portion of the prepreg is from 10 to 80% by mass.
 2. The methodaccording to claim 1 for manufacturing a prepreg, wherein in the mass ofthe solid in the reinforcing fiber base material obtained in the step(I), the ratio of the reinforcing fibers is from 80 to 100% by mass. 3.The method for manufacturing a prepreg according to claim 1, wherein thestep (I) of dispersing a reinforcing fiber bundle to obtain areinforcing fiber base material is the following (a): (a) comprisingstep (i) of charging a reinforcing fiber bundle to a dispersion medium,step (ii) of preparing a slurry in which reinforcing fibers forming thereinforcing fiber bundle are dispersed in the dispersion medium, step(iii) of transporting the slurry, and step (iv) of removing thedispersion medium from the slurry to produce a papermaking base materialcontaining reinforcing fibers, wherein C1/C2 is from 0.8 to 1.2 wherethe mass content of the reinforcing fibers in the slurry prepared in thestep (ii) is expressed by C1, and the mass content of the reinforcingfibers in the slurry at the time of the commencement of the step (iv) isexpressed by C2.
 4. The method for manufacturing a prepreg according toclaim 1, wherein the step (I) of dispersing a reinforcing fiber bundleto obtain a reinforcing fiber base material is the following (b): (b)comprising step (i) of charging a reinforcing fiber bundle to adispersion medium, step (ii) of preparing a slurry in which reinforcingfibers forming the reinforcing fiber bundle are dispersed in thedispersion medium, step (iii) of transporting the slurry, and step (iv)of removing the dispersion medium from the slurry to produce apapermaking base material containing reinforcing fibers, wherein thesteps (i) to (iv) are carried out online and the level H1 of the surfaceof the slurry in the step (ii) is higher than the level H2 of thesurface of the slurry in the step (iv).
 5. The method for manufacturinga prepreg according to claim 1, wherein the step (I) of dispersing areinforcing fiber bundle to obtain a reinforcing fiber base material isthe following (c): (c) comprising step (i) of charging a reinforcingfiber bundle to a dispersion medium, step (ii) of preparing a slurry inwhich reinforcing fibers forming the reinforcing fiber bundle aredispersed in the dispersion medium, step (iii) of transporting theslurry, and step (iv) of removing the dispersion medium from the slurryto produce a reinforcing fiber base material, wherein the steps (i) and(ii) are carried out in a dispersion vessel, the step (iv) is carriedout in a papermaking vessel, the step (iii) is carried out in atransport portion that connects the dispersion vessel and thepapermaking vessel, and the slurry is transported in a laminar flowstate or in a transition region state from a laminar flow to a turbulentflow in the transport portion.